Costume custom (5)
I believe the answer is:
habit
This clue is a double definition.
'costume' is the first definition.
(I know that habit is a type of costume)
'custom' is the second definition.
(I know that habit is a type of custom)
(Other definitions for habit that I've seen before include "Custom; riding dress" , "Breaking this is hard" , "Routine - clothing" , "Ingrained behaviour" , "Monk's garb" .)