Gorillas and gibbons (4)
I believe the answer is:
apes
'gorillas and gibbons' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for apes that I've seen before include "Species of primate" , "Parrots" , "Peas (anag)" , "Imitates in every aspect" , "Imitates like primates" .)