Parrots? A nuisance, for the most part (4)
I believe the answer is:
apes
'parrots?' is the definition.
(parrot is a kind of ape)
'a nuisance for the most part' is the wordplay.
'nuisance' becomes 'pest' (I've seen this before).
'for the most part' means to remove the last letter.
'pest' with its final letter removed is 'pes'.
'a'+'pes'='APES'
(Other definitions for apes that I've seen before include "Species of primate" , "Peas (anag)" , "Imitates in every aspect" , "Imitates like primates" , "Large primates" .)