Nonsense; plant (7)
I believe the answer is:
rhubarb
This clue is a double definition.
'nonsense' is the first definition.
(rhubarb can mean nonsense or rubbish)
'plant' is the second definition.
(rhubarb is a kind of plant)
(Other definitions for rhubarb that I've seen before include "Possibly sweet" , "Actors' muttering to simulate conversation" , "Rheum rhaponticum" , "bitter stuff" , "Reddish leafstalks cooked and eaten as fruit" .)