Quietly tell ecclesiastical dignitary (7)
I believe the answer is:
prelate
'ecclesiastical dignitary' is the definition.
(type of dignitary in the church)
'quietly tell' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'tell' becomes 'relate' (as in to tell or relate a story).
'p'+'relate'='PRELATE'
(Other definitions for prelate that I've seen before include "e.g. Bishop" , "Bishop perhaps" , "Church high-ranker" , "priest" , "Cleric" .)