Tune for church service (3,5)
I believe the answer is:
air force
'service' is the definition.
(air force is a kind of service)
'tune for church' is the wordplay.
'tune' becomes 'air' (I've seen this before).
'church' becomes 'ce' (abbreviation for Church of England).
'air'+'for'+'ce'='AIR FORCE'
(Other definitions for air force that I've seen before include "Country's military planes" , "Armed service" , "Kind of blue" , "Junior service" , "A country's flying service" .)