Work trapeze artistes are ill-advised to have (5)
I believe the answer is:
nonet
'work' is the definition.
(musical work for nine musicians)
I don't understand the rest of the clue.
(Other definitions for nonet that I've seen before include "Group of nine musicians" , "group composition" , "Piece for nine payers" , "Piece for group" , "Composition for nine instruments" .)