Area near the altar (4)
I believe the answer is:
apse
'area near the altar' 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 "Recess at east end of church" , "room for an altar" , "Semicircular end of a church, behind the altar" , "Semicircular recess in church" , "Rounded end of building" .)