This may be hot - had better put on a raised bar inside (7)
I believe the answer is:
mustard
'this may be hot had better put on a raised bar inside' is the definition.
The answer and definition can be both plants as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for mustard that I've seen before include "Powdered seeds used to make condiment" , "Dark yellow" , "Standard of keenness" , "Hot-tasting condiment" , "Proverbially keen condiment" .)