Bob to take off clothes in part of church (4)
I believe the answer is:
apse
'part of church' is the definition.
(part of a church building)
'bob to take off clothes' is the wordplay.
'bob' becomes 's' (abbreviation for shilling - 'bob' before 1971).
'to take off' becomes 'ape' (both can mean to imitate).
'clothes' means one lot of letters goes inside another (some letters clothe or cover others).
's' going within 'ape' is 'APSE'.
'in' acts as a link.
(Other definitions for apse that I've seen before include "Large recess in church" , "Church recess in lapsed condition" , "Recess with domed rof in a church" , "room for an altar" , "Projection to the east end of a church" .)