Vaulted alcove (4)
I believe the answer is:
apse
'vaulted 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 "place in church" , "part of cathedral" , "Rounded end of building" , "Strange peas in the church recess" , "Recess with domed rof in a church" .)