Work trapeze artists are ill-advised to have? (5)
I believe the answer is:
nonet
'work' is the definition.
(musical work for nine musicians)
I cannot understand how the rest of the clue works.
(Other definitions for nonet that I've seen before include "group composition" , "Composition for nine performers" , "Musical composition -- tonne (anag)" , "Group of nine musicians" , "Composition for nine voices" .)