Turned to church as an authority (6)
I believe the answer is:
source
'an authority' is the definition.
(thesaurus)
'turned to church' is the wordplay.
'turned' becomes 'sour' (synonyms).
'to church' becomes 'CE' (abbreviation for Church of England).
'sour'+'ce'='SOURCE'
'as' is the link.
(Other definitions for source that I've seen before include "Place or person where something begins" , "Well" , "Origin, starting-point" , "Beginning to add" , "Find" .)