Nicotine plant (7)
I believe the answer is:
tobacco
'nicotine plant' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tobacco that I've seen before include "make a cot cob from this plant" , "Controversial plant grown commercially" , "Leaves to smoke" , "Smokable plant" , "Smoked narcotic plant" .)