Poison several crowding one bed (8)
I believe the answer is:
nicotine
'poison' is the definition.
(nicotine is a kind of poison)
'several crowding one bed' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'bed' could be 'cot' (cot is a type of bed) and 'cot' is found in the answer.
The remaining letters 'nine' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nicotine that I've seen before include "Once in it (anag)" , "Not nice, I change to cigarette substance" , "Once in it, strangely, one smokes it" , "Material found in tobacco used as an insecticide" , "Chief constituent of tobacco" .)