Cheap seats provide part of church (4)
I believe the answer is:
apse
'part of church' is the definition.
(part of a church building)
'cheap seats provide' is the wordplay.
'provide' indicates the answer is hidden within the clue.
'APSE' is hidden in the letters of 'cheap seats'.
(Other definitions for apse that I've seen before include "Where the altar is usually found in a church" , "In sacred space" , "Architectural feature in a church" , "Part of a church with the altar" , "Recess at east end of church" .)