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