Fruit eaten by little monkeys (5)
I believe the answer is:
lemon
'fruit' is the definition.
(I know that lemon is a fruit)
'eaten by little monkeys' is the wordplay.
'eaten by' says the answer is hidden in the clue.
'LEMON' can be found hidden inside 'little monkeys'.
(Other definitions for lemon that I've seen before include "Yellow citrus fruit with acid taste" , "Melon (anag)" , "Fruit-tree" , "Acidic fruit" , "Fruit - as an answer it's unsatisfactory" .)