I'm not sure I understand; let me try...
You are working in this case within a single library. One of the fields is a Link to Entry field pointed back into this same library, allowing an entry to link to one or more other entries in the library, yes? In addition, you want the value of a field in a linked entry to appear in the outer entry, yes?
Well, if I've understood that correctly, then first, it must be a one-to-many relationship, so that there is a unique entry whose field1 value is to be referenced.