Troglodyte (7)
I believe the answer is:
caveman
'troglodyte' is the definition.
(I know that caveman is a type of troglodyte)
This is all the clue.
(Other definitions for caveman that I've seen before include "he has primitive habits" , "Prehistoric male" , "Troglodyte" , "Prehistoric chap" , "old-timer?" .)