Row over church service (6)
I believe the answer is:
tierce
'service' is the definition.
(thesaurus)
'row over church' is the wordplay.
'row' becomes 'tier' (tier is a kind of row).
'over' says to put letters next to each other.
'church' becomes 'ce' (abbreviation for Church of England).
'tier'+'ce'='TIERCE'
(Other definitions for tierce that I've seen before include "service" , "parrying position" .)