Embargo on unconventional missile (9)
I believe the answer is:
boomerang
'missile' is the definition.
(I know that boomerang is a type of missile)
'embargo on unconventional' is the wordplay.
'unconventional' indicates an anagram.
'embargo'+'on'='embargoon'
'embargoon' anagrammed gives 'BOOMERANG'.
(Other definitions for boomerang that I've seen before include "Backfire" , "Australian throwing stick" , "Curved throwing stick" , "Aboriginal throwing stick" , "Aboriginal weapon" .)