Those in service favouring church society (6)
I believe the answer is:
forces
'those in service' is the definition.
(armed forces)
'favouring church society' is the wordplay.
'favouring' becomes 'for' (I've seen this before).
'church' becomes 'CE' (abbreviation for Church of England).
'society' becomes 's' (common abbreviation in names of organisations).
'for'+'ce'+'s'='FORCES'
(Other definitions for forces that I've seen before include "Compels or coerces" , "Compels someone to do something" , "Prizes" , "Military and police, say" , "Compels, obliges" .)