Caught greeting fellow ancestor (7)
I believe the answer is:
caveman
'ancestor' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for caveman that I've seen before include "he has primitive habits" , "Prehistoric chap" , "Van came carrying old cliff dweller" , "Neanderthal person" , "Prehistoric male" .)