Offence of minister losing head? (5)
I believe the answer is:
Here is my best explanation:
'offence' is the definition.
'minister losing head?' is the subsidiary indication.
'minister' becomes 'parson' ('parson' can be a synonym of 'minister').
'losing head?' means to remove the first letter.
'parson' with its first letter taken off is 'arson'.
'of' is the link.
(Other definitions for arson that I've seen before include "It may get you in court", "serious offence", "It's a crime", "Felonious burning of property", "Malicious burning to destroy property", "Crime of fire-setting (5)", "Incendiary crime", "Fire-raiser's crime", "The crime of fire-setting" and "The crime of fire-raising".)