Diviner decree replacing one abbey's number two released (9)
I believe the answer is:
predictor
'diviner' is the definition.
(thesaurus)
'decree replacing one abbey's number two released' is the wordplay.
I cannot quite understand how this works, but
'decree' could be 'edict' (synonyms) and 'edict' is found within the answer.
'one' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
This explanation may well be incorrect...
(Other definitions for predictor that I've seen before include "Someone who foretells events" , "one might have expected it?" .)