Established church in French region (8)
I believe the answer is:
provence
'french region' is the definition.
(I've seen this before)
'established church' is the wordplay.
'established' becomes 'proven' (similar in meaning).
'church' becomes 'CE' (abbreviation for Church of England).
'proven'+'ce'='PROVENCE'
'in' is the link.
(Other definitions for provence that I've seen before include "Area of SE France" , "Region of southeast France" , "Never cop this French region" , "somewhere in France" , "Even crop is badly produced in France" .)