States opposed banning latest drug (5)
I believe the answer is:
avers
'states opposed banning' is the definition.
'avers' can be an answer for 'states' (to aver is to declare or state). I am unsure of the 'opposed banning' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for avers that I've seen before include "States positively" , "Swears" , "Declares to be true" , "States firmly - really raves" , "Alleges, asserts" .)