Chemical drugs containing poisonous element (6)
I believe the answer is:
potash
'chemical' is the definition.
(I know that potash is a type of hydrated oxide)
'drugs containing poisonous element' is the wordplay.
I cannot quite see how this works, but
'drugs' could be 'pot' (slang term for mariujana) and 'pot' is located in the answer.
'element' could be 'as' (As is an example) and 'as' is found in the answer.
A single letter 'h' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for potash that I've seen before include "Caustic stuff" , "feed in bed?" , "Agricultural chemical" , "chemical compound" , "The strange pathos of a potassium compound" .)