Composition for nine performers (5)
I believe the answer is:
nonet
'composition for nine performers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nonet that I've seen before include "Music for nine instruments or voices" , "Band's" , "Piece for nine performers" , "Composition for nine voices" , "Musical work for a set number of performers" .)