What drug dealer may do in kitchen vessel (8)
I believe the answer is:
stockpot
'vessel' is the definition.
(pot for preparing stock)
'what drug' is the wordplay.
'what' becomes 'stock' (I can't justify this - if you can you should give a lot more credence to this answer).
'drug' becomes 'pot' (slang term for cannabis).
'stock'+'pot'='STOCKPOT'
'dealer may do in kitchen' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for stockpot that I've seen before include "kitchen utensil" , "Casserole" , "Cooking vessel for soups" , "gravy container" , "source of many soups" .)