Missing nothing in breaking the law (4)
I believe the answer is:
awol
'missing' is the definition.
(I've seen this before)
'nothing in breaking the law' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'in' indicates putting letters inside.
'breaking' indicates anagramming the letters.
'law' with letters rearranged gives 'awl'.
'o' inserted within 'awl' is 'AWOL'.
(Other definitions for awol that I've seen before include "Army offence of being missing from duty, briefly" , "On the lam" , "'Absent without permission, initially (4)'" , "gone missing" , "Not present when supposed to be" .)