Tool used to break the law (3)
I believe the answer is:
awl
'tool' is the definition.
(awl is a kind of tool)
'to break the law' is the wordplay.
'to break' is an anagram indicator (letters broken up and rearranged).
'law' with letters rearranged gives 'AWL'.
'used' acts as a link.
(Other definitions for awl that I've seen before include "Hole-making tool" , "Something needed for boring jobs" , "Hole-piercing tool" , "scribe" , "has its use at last" .)