Tools that break laws (4)
I believe the answer is:
awls
'tools' is the definition.
(awl is a kind of tool)
'break laws' is the wordplay.
'break' is an anagram indicator.
'laws' with letters rearranged gives 'AWLS'.
'that' acts as a link.
(Other definitions for awls that I've seen before include "Laws about boring tools (4)" , "Small piercing tools" , "Tools for punching small holes" , "Pointed hand-tools" .)