Strict member of the clergy turned up in diocese (6)
I believe the answer is:
severe
'strict' is the definition.
(thesaurus)
'member of the clergy turned up in diocese' is the wordplay.
'member of the clergy' becomes 'rev'.
'turned up' says the letters should be written backwards.
'in' means one lot of letters goes inside another.
'diocese' becomes 'see' (I've seen this before).
'rev' written backwards gives 'ver'.
'ver' placed within 'see' is 'SEVERE'.
(Other definitions for severe that I've seen before include "Forbidding in action or appearance" , "Stern or stringent" , "Serious or strict" , "Draconian" , "Austere, serious" .)