Reluctant to be seen in church dress (6)
I believe the answer is:
clothe
'dress' is the definition.
(I know that dress can be written as clothe)
'reluctant to be seen in church' is the wordplay.
'reluctant' becomes 'loth' (if you are loth to do something you are reluctant).
'to be seen in' indicates putting letters inside.
'church' becomes 'CE' (abbreviation for Church of England).
'loth' inserted into 'ce' is 'CLOTHE'.
(Other definitions for clothe that I've seen before include "Remote area in Mongolia/China" , "Attire" , "Provide with garments" , "Fit out with garments" , "Dress (someone)" .)