Blessing reformed brute accepting one reduced sphere of action (4,2,4)
I believe the answer is:
urbi et orbi
'blessing' is the definition.
(I have seen 'papal blessing' mean 'urbi et orbi' so perhaps 'blessing' could also mean 'urbi et orbi')
'reformed brute accepting one reduced sphere of action' is the wordplay.
'reformed' is an anagram indicator.
'accepting' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'reduced' means to remove the last letter.
'sphere of action' becomes 'orbit' (I've seen this before).
'brute' anagrammed gives 'urbet'.
'urbet' enclosing 'i' is 'urbiet'.
'orbit' with its final letter taken off is 'orbi'.
'urbiet'+'orbi'='URBI ET ORBI'
(Other definitions for urbi et orbi that I've seen before include "(In Pope's blessing) to the city and to the world" , "papal blessing" , "Pontiff's To the City and the World" .)