Returning, arrest outlaw (3)
I believe the answer is:
ban
'outlaw' is the definition.
(banning is a kind of outlawing)
'returning arrest' is the wordplay.
'returning' shows that the letters should be reversed in order.
'arrest' becomes 'nab' (synonyms).
'nab' back-to-front is 'BAN'.
(Other definitions for ban that I've seen before include "the calling of young vassals" , "outlaw" , "Stop" , "Veto" , "Embargo" .)