Crime of clergyman losing head (5)
I believe the answer is:
arson
'crime' is the definition.
(I've seen this before)
'clergyman losing head' is the wordplay.
'clergyman' becomes 'parson' (parson is a kind of clergyman).
'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 "The act of firing" , "major crime" , "criminal fire-raising" , "Malicious fire-raising" , "Act of a pyromaniac" .)