Parrot or full-sized old primates (6)
I believe the answer is:
apemen
'parrot or full-sized old primates' is the definition.
I know nothing about this answer so I can't judge whether this works.
'parrot or full-sized old primates' is the wordplay.
I cannot quite see how this works, but
'parrot' could be 'ape' (both can mean to imitate) and 'ape' is found in the answer.
'primates' could be 'men' (man is a kind of primate) and 'men' is located 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 apemen that I've seen before include "Our predecessors" , "Extinct human ancestors" .)