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

I believe the answer is:
health insurance
'cover' is the definition.
(I've seen this before)
'pm maintaining line in sand shortly seizing old city church' is the wordplay.
I cannot quite see how this works, but
'line' could be 'l' (used when specifying particular lines from a poem) and 'l' is found in the answer.
'pm' could be 'heath' (prime minister Edward Heath) and 'heath' is found within the remaining letters.
'in' is within the answer.
'city' could be 'ur' (ancient Sumerian city state) and 'ur' is present in the answer.
'church' could be 'ce' (abbreviation for Church of England) and 'ce' is found within the answer.
The remaining letters 'san' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for health insurance that I've seen is " cover".)
