Criminal embargo on returning weapon (9)
I believe the answer is:
boomerang
'returning weapon' is the definition.
(weapon which returns when thrown)
'criminal embargo on' is the wordplay.
'criminal' indicates anagramming the letters.
'embargo'+'on'='embargoon'
'embargoon' with letters rearranged gives 'BOOMERANG'.
(Other definitions for boomerang that I've seen before include ""It keeps coming back"" , "Aboriginal throwing stick" , "Backfire" , "Aboriginal projectile" , "Australian throwing stick" .)