Fruit mostly for ape (5)
I believe the answer is:
orang
'for ape' is the definition.
(orang-utan)
'fruit mostly' is the wordplay.
'fruit' becomes 'orange' (orange is a kind of fruit).
'mostly' means to remove the last letter (most but not all of the word).
'orange' with its last letter taken off is 'ORANG'.
(Other definitions for orang that I've seen before include "- - -utan" , "Forest-dweller with red hair" , "Primate" , "Wild animal briefly appeared" , "Short tree-dweller" .)