The crime of a hard hearted lad (5)
I believe the answer is:
arson
'the crime' is the definition.
(I've seen this before)
'a hard hearted lad' is the wordplay.
'hearted' means to look at the middle letters.
'lad' becomes 'son'.
The central letters of 'hard' are 'ar'.
'ar'+'son'='ARSON'
'of' is the link.
(Other definitions for arson that I've seen before include "major crime" , "Malicious fire-raising" , "Criminal activity" , "Crime of fire raising" , "Malicious fire-lighting" .)