Whole piece from composer, it needs going over (6)
I believe the answer is:
entire
'whole' is the definition.
(similar in meaning)
'piece from composer it needs going over' is the wordplay.
'piece from' indicates the answer is hidden within the clue.
'going over' is a reversal indicator.
'eritne' is hidden in the letters of 'composer it needs'.
'eritne' reversed gives 'ENTIRE'.
(Other definitions for entire that I've seen before include "Whole; unbroken" , "Full and complete" , "in one piece" , "Unmitigated" , "Utter" .)