Poisonous mixture of drinks? (9)
I believe the answer is:
snakebite
I believe this clue is a double definition.
'poisonous' is the first definition.
(I've seen this before)
'mixture of drinks?' is the second definition.
(I've seen this before)
(Other definitions for snakebite that I've seen before include "Drink made of lager and cider" , "Cider and lager - it could be poisonous" , "hooch" , "strong drink" , "Cider-lager drink" .)