Malt liquor, including very mature drink (8)
I believe the answer is:
beverage
'drink' is the definition.
('beverage' can be a synonym of 'drink')
'malt liquor including very mature' is the wordplay.
'malt liquor' becomes 'beer' (I've seen this before).
'including' means one lot of letters goes inside another.
'very' becomes 'v' (abbreviation).
'mature' becomes 'age' ('age' can be a synonym of 'mature').
'beer' going around 'v' is 'bever'.
'bever'+'age'='BEVERAGE'
(Other definitions for beverage that I've seen before include "Liquid for drinking" , "Any drink, say a beer" , "Non-alcoholic drink" , "Liquid refreshment" , "such as a Frappuccino" .)