Despicable individuals raised money to grow poisonous plant (9)
I believe the answer is:
toadstool
'plant' is the definition.
(toadstool is a kind of plant)
'despicable individuals raised money' is the wordplay.
'despicable individuals' becomes 'toads' (I can't justify this - if you can you should believe this answer much more).
'raised' says the letters should be written backwards (going up in a down clue).
'money' becomes 'loot' (loot is a kind of money).
'loot' reversed gives 'tool'.
'toads'+'tool'='TOADSTOOL'
'to grow poisonous' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for toadstool that I've seen before include "Common fungus" , "Support for little people" , "Plant akin to mushroom" , "Inedible fungus" , "what's poisonous maybe" .)