Molasses plant a class included (7)
I believe the answer is:
treacle
'molasses' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for treacle that I've seen before include "Something cloyingly sweet" , "Contrived sentimentality - sticky substance" , "Sweet, sticky stuff" , "Sweet, black viscous substance" , "Saplike stuff" .)