Piece for soloist and orchestra (8)
I believe the answer is:
concerto
'piece for soloist and orchestra' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for concerto that I've seen before include "10 [COMPOSITION]" , "Musical work" , "Orchestral composition" , "Orchestral work for solo instrument" , "Musical composition" .)