Church alcove (4)
I believe the answer is:
apse
'church alcove' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for apse that I've seen before include "inside church?" , "Church recess with domed or arched roof" , "space for altar" , "Recess at east end of church" , "Part of a church with the altar" .)