Heartless goon at boundary commits crime (7)
I believe the answer is:
offence
'crime' is the definition.
(offence is a kind of crime)
'heartless goon at boundary' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'goon' becomes 'oaf' (synonyms).
'at boundary' becomes 'fence' (I can't explain this - if you can you should give a lot more credence to this answer).
'oaf' with its centre removed is 'of'.
'of'+'fence'='OFFENCE'
'commits' is the link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for offence that I've seen before include "Crime; insult" , "Transgression" , "taken by one insulted" , "Hurt; military attack" , "Crime - umbrage" .)