Beware of Caligula — he’s a brute (7)
I believe the answer is:
caveman
'a brute' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'beware of caligula he's' is the wordplay.
I cannot really see how this works, but
'beware' could be 'cave' (old-fashioned term meaning 'look out') and 'cave' is found within the answer.
'he' could be 'man' (I've seen this in another clue) and 'man' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for caveman that I've seen before include "Troglodyte" , "Van came carrying old cliff dweller" , "he has primitive habits" , "Prehistoric chap" , "Prehistoric male" .)