A pile of green apples (3)
I believe the answer is:
nap
'a pile' is the definition.
(thesaurus)
'of green apples' is the wordplay.
'of' indicates the answer is hidden within the clue.
'NAP' is hidden in the letters of 'green apples'.
(Other definitions for nap that I've seen before include "Short sleep on fuzzy fabric surface" , "Sleep - card game - fibres on a snooker table" , "Short raised fibres on cloth on snooker table" , "Take forty winks" , "A brief informal sleep" .)