Crime Harry scorns regularly (5)
I believe the answer is:
arson
'crime' is the definition.
(I've seen this before)
'harry scorns regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'harry'+'scorns'='harryscorns'
The alternating letters of 'harryscorns' are 'ARSON'.
(Other definitions for arson that I've seen before include "Crime of fire raising" , "The act of firing" , "Fire-raising crime" , "Act of a pyromaniac" , "Criminal pyromania" .)