Served up, magnificent drink (5)
I believe the answer is:
lager
'drink' is the definition.
(lager is a kind of drink)
'served up magnificent' is the wordplay.
'served up' says the letters should be written backwards.
'magnificent' becomes 'regal' (regal can mean magnificent or grand).
'regal' backwards is 'LAGER'.
(Other definitions for lager that I've seen before include "Regal kind of beer" , "Effervescent beer" , "Continental beer" , "Bottom-fermented beer" , "Light-coloured beer" .)