Tell clergyman not to start (6)
I believe the answer is:
'tell' is the definition.
(as in to tell or relate a story)
'clergyman not to start' is the wordplay.
'clergyman' becomes 'prelate' (prelate is a kind of clergyman).
'not to start' means to remove the first letter.
'prelate' with its initial letter taken away is 'RELATE'.
(Other definitions for relate that I've seen before include "Recount" , "Sympathise" , "Narrate in Tralee" , "Tell (a story)" , "Show a connection between (things)" .)