There's no smoke without it (7)
I believe the answer is:
tobacco
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for tobacco that I've seen before include "Weed dangerous to health" , "Dangerous plant" , "make a cot cob from this plant" , "(Treated leaves of) American plant" , "Leaves to smoke" .)