Repeated thanks to all entrants (and repeated apologies for the delay). My opinions are below, and the result at the end.
Luciano
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Pan (the pro):
Letter by grand American conservative is worthless (8)
NU + G + A TORY; def = worthless
-- Indicating NU (the Greek letter) simply with 'letter' seems a bit lazy and not very helpful to the solver. The rest is okay, but nothing special.
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David:
Industrious young rat considered trifling (8)
YOUNGRAT anag; def = considered trifling
-- I can go with 'industrious' as an anagram indicator. 'considered trifling' seems a wee bit bloated as a definition, but it works. The anagram fodder is very good. The surface reading is the clue's weakest part. P=
Croc certified as child-friendly in the Big Apple? Pull the other one! (8)
child-friendly = U, so [U GATOR] in NY; def = pull the other one (not sure how)
-- I'm okay with 'U GATOR' as indicated in the clue. The definition doesn't do it for me, however: although 'nugatory' might mean 'not valid', 'pull the other one' as a definition is a stretch; it is certainly a vaguely connected sentiment, but is not a definition (imagine a sentence with 'nugatory' in it, and replace that word with 'pull the other one' while retaining the meaning and grammatical correctness of the sentence; I can't). P-
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Duke:
Small reptile on the border of uptown, in New York (8)
border of uptown = U, so [U GATOR] in NY; def = small
-- I would have left out 'the', so as to imply 'a' (one) border of 'uptown', rather than 'the' (only) border ('the western border' would have been fine). The definition is okay, but lacks oomph. The surface reading is a bit awkward. P-
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Kevin:
Fruitless nut- or yellow cakes Gina's frosting (8)
[NUT OR Y] around GA (Gina's frosting); def = fruitless
-- The wordplay is fine (I especially like how GA is got). The surface reading is not wonderful; is a yellow cake a thing (other than a cake that's yellow), and why are we talking about a nutcake versus a yellow cake, and who is this mysterious Gina? I'm being a bit facetious here, but the surface reading does look greatly forced. P-
So against a crocodilian, a club is useless (8)
so = nu (Yiddish), so NU + GATOR + Y (YM(W)CA); def = useless
-- 'so' = 'nu' was vaguely familiar to me (it might have been used in another clue in the group some time back). The wordplay is good. I would have liked a colon (or even a comma) after 'so', but that's me being picky. P=
They ultimately list weapon "Returned in non-operative condition" (8)
Y + ROTA + GUN rev; def = in non-operative condition
-- All good in terms of wordplay. The definition seems rather strained, but obviously fits in with the surface reading. P-
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Rob:
Fruitless nutty confection spilled over line (8)
NOUGAT anag + RY; def = fruitless
-- This is an indirect anagram (where you provide a definition of the (here, partial) anagram fodder, rather than having those letters visible in the clue). I'm not a fan of that. P-
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The winner is Kevin with his club-resistant crocodilian. Second is David with his harshly regarded diligent rodent.