Expensive policy not popular for part of church (7)
I believe the answer is:
steeple
'for part of church' is the definition.
(I've seen this before)
'expensive policy not popular' is the wordplay.
'expensive' becomes 'steep' (I've seen this before).
'policy' becomes 'line' (the party line is a party's policy on something).
'not' indicates named letters should be taken away.
'popular' becomes 'in' ('in' can mean trendy).
'line' with 'in' taken away is 'le'.
'steep'+'le'='STEEPLE'
(Other definitions for steeple that I've seen before include "Sort of chase" , "part of church" , "Tall building" , "that the church may be under" , "Pointed structure" .)