Abbey section (4)
I believe the answer is:
apse
'abbey section' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for apse that I've seen before include "inside church?" , "place in church" , "Recess at eastern end of a church" , "Peas (anag) - found in church" , "Semicircular end of a church, behind the altar" .)