Unwilling to wear Church attire (6)
I believe the answer is:
clothe
'attire' is the definition.
(I've seen this before)
'unwilling to wear church' is the wordplay.
'unwilling' becomes 'loth' (similar in meaning).
'to wear' means one lot of letters goes inside another (to wear something is to be covered up by it).
'church' becomes 'CE' (abbreviation for Church of England).
'loth' put within 'ce' is 'CLOTHE'.
(Other definitions for clothe that I've seen before include "Put garments onto" , "Invest" , "robe" , "apparel" , "Equip" .)