Edge into church at a war zone (6)
I believe the answer is:
crimea
'war zone' is the definition.
(I've seen this before)
'edge into church at a' is the wordplay.
'edge' becomes 'rim' (rim is a kind of edge).
'into' is an insertion indicator.
'church' becomes 'CE' (abbreviation for Church of England).
'at' means one lot of letters go next to another.
'rim' inserted within 'ce' is 'crime'.
'crime'+'a'='CRIMEA'
(Other definitions for crimea that I've seen before include "Area of Ukraine" , "'Ukrainian peninsula, site of a 19th-century war (6)'" , "Peninsula in Ukraine where the Light Brigade charged" , "Ukraine peninsula, scene of war (1853-6)" , "part of the Ukraine" .)