Complete costume for musicians (8)
I believe the answer is:
ensemble
This clue is a double definition.
'complete costume' is the first definition.
(I've seen this in another clue)
'musicians' is the second definition.
(I've seen this before)
'for' is the link.
(Other definitions for ensemble that I've seen before include "Group of musicians or a co-ordinated outfit" , "supporting cast" , "Group of entertainers" , "Group of musicians playing together" , "Small group or complete costume" .)