Dear Scott, John, and Adrian ~
There appears to be no question that Joan de Clopton married Sir Walter de Walcote (living 1355), of Walcott, Gunton, and Little Snoring, Norfolk, and Roger de Beauchamp (the younger), Knt. (died 1374). The only question is if Joan de Clopton was the mother of Sir Roger de Beauchamp's son and heir, Roger, born in 1362.
Sir Walter de Walcote presented to the church of Gunton, Norfolk in 1352. Reference: Blomefield, Essay towards a Topog. Hist. of Norfolk 8 (1808): 122.
Sir Walter de Walcote and Joan his wife were involved in a Norfolk fine dated Hilary term 1354. See the following weblink for the original fine:
http://aalt.law.uh.edu/AALT6/CP25_1/Norf/CP25_1_166/IMG_0139.htm
Walter de Walcote was living 6 July 1355. Reference: Cal. Patent Rolls, 1354–1358 (1909): 209, which is available at the following weblink:
https://babel.hathitrust.org/cgi/pt?id=mdp.39015031079323;view=1up;seq=221
In 29 Edward III [1355-1356] Walter de Walcote, knight, and Thomas de Walcote, clerk, had license to grant the advowson of the church of Hempstead by Ingham to John de Derby, clerk, and John de Chikewell of London, the said Walter retaining lands in Walcott, Gunton, and Snoring, Norfolk. Online reference:
http://discovery.nationalarchives.gov.uk/details/r/C7575274
Sir Roger de Beauchamp and Joan, widow of Sir Walter de Walcote, were evidently married before 1372, in which year he presented to the church of Gunton, Norfolk. Reference: Blomefield, Essay towards a Topog. Hist. of Norfolk 8 (1808): 123.
Sir Roger de Beauchamp died shortly before 15 May 1374, when administration on his estate was granted to his widow, Joan.
Joan was still living 1 July 1395 (date of fine). See the following weblink for the original fine:
http://aalt.law.uh.edu/AALT6/CP25_1/Norf/CP25_1_168_176-181/IMG_0307.htm
Walter Rye, Some Rough Materials for a History of the Hundred of North Erpingham 1 (1883): 79–80, 86-88 gives a rather good overview of the records which concern this family, including some of the items cited above. Among other things, he includes a record involving Sir Walter de Walcote and Sir John de Norwich dated June 1355.
On pages 79-80, he quotes an "old pedigree" which reads in part: "Sir Walter de Gunton, a strong and handsom knight, who, in his youth, married one Adelina, and by her had an only daughter and heir, maried to Sir Walter de Walcote, Knt., from whom came Walter de Walcote, who maried Joane, daughter of William Clopton. They had issue four daughters and heirs, of whom the 2nd, Margaret, was maried to Sir Robert Berney, Knt., in the time of King Edward III." END OF QUOTE.
Elsewhere I find that Blomefield, Essay towards a Topog. Hist. of Norfolk 8 (1808): 120 gives the following additional information:
"Sir Walter de Gunton, by Adelicia his wife, left a daughter and heir, Milecentia, who brought it [the manor of Gunton] by marriage to Sir Walter de Walcot, whose son, Sir Walter, marrying Joan, daughter and heir of William, 2d son of Sir Sir William Clopton, left 4 daughters and coheirs; Margaret, the wife of Sir Robert Berney of Wichingham, relict of Roger de Welesham; Elizabeth, wife of Ralph Bray, or rather of William Wylton of Wichampton in Norfolk; Catherine, of John Dorward, Esq.; and Margery, a nun, at Carhow abbey near Norwich. Joan, after the decease of her husband, Walcot, married Sir Roger Beauchamp; and on May 15, 1374, letters of administrations of all the goods, &c. of Sir Roger Beauchamp were granted to her." END OF QUOTE.
The above information may be viewed at the following weblink:
https://books.google.com/books?id=k9wvAAAAYAAJ&pg=PA120
I don't have access to Rye, Norfolk Families, 1911, p. 971, which allegedly states that Walter de Walcote died in 1366. If someone has access to this book, perhaps they can quote exactly what document Mr. Rye cites to prove this statement. Since Complete Peerage does not cite corresponding contemporary documentation, Mr. Rye's statement may well be in error. The records cited above indicate only that Sir Walter de Walcote was living in 1352, 1354, 1355, and 1355-56.
In answer to Adrian's comment, Complete Peerage is wrong to assign Joan de Clopton as a wife of Sir Roger de Beauchamp the elder, who died in 1380. My research shows that Sir Roger de Beauchamp the elder was surviving by his 2nd wife, Margaret de Carew (died 1394), widow of Sir Thomas de Grandison, K.G., 4th Lord Grandison. Inasmuch as Joan de Clopton was still living in 1395, she obviously can not be either the wife or the widow of the elder Sir Roger.
In answer to Scott's question, as I indicated in my first post in this thread, the various available sources indicate that Joan de Clopton was the daughter of William de Clopton, not Walter de Clopton.