Advanced drink plant (4)
I believe the answer is:
arum
'plant' is the definition.
(arum is a kind of plant)
'advanced drink' is the wordplay.
'advanced' becomes 'a'.
'drink' becomes 'rum' (rum is a kind of drink).
'a'+'rum'='ARUM'
(Other definitions for arum that I've seen before include "genus of plants" , "Perennial" , "Plant like cuckoo pint" , "plant with a white spathe" , "Plant of the family Araceae, eg lords-and-ladies" .)