Formal note about a church dignitary (7)
I believe the answer is:
primate
'church dignitary' is the definition.
'formal note about a' is the wordplay.
'formal' becomes 'prim' (I've seen this in other clues).
'note' becomes 'te' (**).
'about' means one lot of letters go next to another.
'te' put after 'a' is 'ate'.
'prim'+'ate'='PRIMATE'
(Other definitions for primate that I've seen before include "Bishop; large mammal" , "Archbishop - monkey, perhaps" , "A permit for a cardinal" , "Mammal such as human" , "senior cleric" .)