Church dignitary heading off sometime soon (4)
I believe the answer is:
anon
'sometime soon' is the definition.
(I've seen this in another clue)
'church dignitary heading off' is the wordplay.
'church dignitary' becomes 'canon' (I've seen this before).
'heading off' means to remove the first letter.
'canon' with its first letter taken off is 'ANON'.
(Other definitions for anon that I've seen before include "prolific author" , "In the near future" , "At another time and with no identity, in short" , "Writer unknown" , "Incognito (abbrev)" .)