Clergyman avoiding parking offence (5)
I believe the answer is:
arson
'offence' is the definition.
(crime of illegally starting a fire)
'clergyman avoiding parking' is the wordplay.
'clergyman' becomes 'parson' (parson is a kind of clergyman).
'avoiding' suggests deleting specific letters.
'parking' becomes 'p' (abbreviation on road signs).
'parson' with 'p' taken away is 'ARSON'.
(Other definitions for arson that I've seen before include "A burning crime" , "Criminal burning of property" , "major crime" , "Illegally firing" , "burning problem" .)