Hit back about law (5)
I believe the answer is:
react
'hit back' is the definition.
(I've seen this before)
'about law' is the wordplay.
'about' becomes 're' (regarding).
'law' becomes 'act' (I've seen this before).
're'+'act'='REACT'
(Other definitions for react that I've seen before include "Take" , "Show opposition" , "Hit back" , "Perform again" , "Respond to something" .)