Basilica sections (5)
I believe the answer is:
apses
'basilica sections' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for apses that I've seen before include "Domed areas in churches" , "Does 'e pass these in churches?" , "Parts of church" , "Domed areas in church, usually where the altars are" , "Domed areas in church, usually where the altar is" .)