Church dignitary's head removed – it's Tell! (6)
I believe the answer is:
relate
'it's tell' is the definition.
(as in to tell or relate a story)
'church dignitary's head removed' is the wordplay.
'church dignitary' becomes 'prelate' (I've seen this before).
'head removed' means to remove the first letter.
'prelate' with its first letter taken away is 'RELATE'.
(Other definitions for relate that I've seen before include "Tell; a counselling service" , "Marriage Guidance - report" , "Show sympathy" , "Give a report or show a connection" , "Tell (a story)" .)