Tell of churchman losing head (6)
I believe the answer is:
Here is my best explanation:
'tell' is the definition.
(relating is a kind of telling)
'churchman losing head' is the subsidiary indication.
'churchman' becomes 'prelate' (I've seen this before).
'losing head' means to remove the first letter.
'prelate' with its initial letter taken away is 'relate'.
'of' is the link.
(Other definitions for relate that I've seen before include "Give account of (story)", "Narrate, tell in detail", "Make a logical or causal connection", "Tell - the marriage guidance people", "Recount", "Marriage Guidance - report", "Tell, narrate", "Empathise", "Tell in Tralee" and "Tell; a counselling service".)