Church area round border in war zone (6)
I believe the answer is:
crimea
'war zone' is the definition.
(I've seen this before)
'church area round border' is the wordplay.
'church' becomes 'CE' (abbreviation for Church of England).
'area' becomes 'a' (maths abbreviation).
'round' indicates putting letters inside.
'border' becomes 'rim' (both can mean an edge).
'ce'+'a'='cea'
'cea' placed around 'rim' is 'CRIMEA'.
'in' is the link.
(Other definitions for crimea that I've seen before include "Peninsula, scene of war 1853-56" , "Peninsula in today's Ukraine, site of an 1853-6 war" , "former war site" , "High-quality black tea" , "Black Sea region" .)