Served up in decanter, alcoholic drink (6)
I believe the answer is:
claret
'drink' is the definition.
(claret is a kind of drink)
'served up in decanter alcoholic' is the wordplay.
'served up' is a reversal indicator (in a down clue, going upwards).
'in' says the answer is hidden in the clue.
'teralc' is hidden within 'decanter alcoholic'.
'teralc' written backwards gives 'CLARET'.
(Other definitions for claret that I've seen before include "Irish county starts the wine" , "Deep red colour" , "Dark purplish-red colour" , "English word for red Bordeaux wine" , "Red Bourdeaux wine" .)