Cover PM maintaining line in sand, shortly seizing old city church (6,9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

( HEATH [reference Edward HEATH {1916 – 2005}, former UK Prime Minister] containing [maintaining] L [line]) + IN + ([ SAN D excluding the final letter [briefly] D ] containing [seizing] UR [old Sumerian city-state in ancient Mesopotamia]) + CE (Church [of England])