Prepare costume (5)
I believe the answer is:
dress
I believe this clue is a double definition.
'prepare' is the first definition.
(I've seen this before)
'costume' is the second definition.
(thesaurus)
(Other definitions for dress that I've seen before include "female garment" , "changing gear" , "Uniform" , "clobber" , "clean > bandage" .)