Tailless simian (3)
I believe the answer is:
ape
'tailless simian' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ape that I've seen before include "Primate resembling a human" , "Mimic the primate" , "Large primate" , "intelligent creature" , "Imitate uncritically" .)