Unknown individual where war is being fought? (4)
I believe the answer is:
zone
'where war is being fought?' is the definition.
(warzone)
'unknown individual' is the wordplay.
'unknown' becomes 'z' (algebra).
'individual' becomes 'one' (an individual is one person).
'z'+'one'='ZONE'
(Other definitions for zone that I've seen before include "Area subject to restrictions, parking say" , "Particular area or sector" , "Area with particular characteristics" , "A defined area as for particular purpose" , "Region; time area" .)