Band costume (6)
I believe the answer is:
outfit
This clue is a double definition.
'band' is the first definition.
(thesaurus)
'costume' is the second definition.
(I know that outfit is a type of dress)
(Other definitions for outfit that I've seen before include "Costume" , "Ensemble of clothes" , "Kit, rig-out" , "Equip for an enterprise" , "Set of clothes or equipment" .)