State of a reactionary priest (4)
I believe the answer is:
aver
'state' is the definition.
(both can mean to declare)
'a reactionary priest' is the wordplay.
'reactionary' shows that the letters should be reversed in order (reactions happen in the opposite direction).
'priest' becomes 'rev'.
'rev' back-to-front is 'ver'.
'a'+'ver'='AVER'
'of' is the link.
(Other definitions for aver that I've seen before include "Declare or insist" , "Declare to be the case" , "Assert to be the case" , "claim" , "Formally state" .)