Piece for seven (6)
I believe the answer is:
septet
'piece for seven' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for septet that I've seen before include "Group of seven performers or singers" , "Musical composition written for seven performers" , "Odd number of players performing" , "G7" , "Seven-piece band" .)