Drink for a sovereign served up (5)
I believe the answer is:
lager
'drink' is the definition.
(lager is a kind of drink)
'sovereign served up' is the wordplay.
'sovereign' becomes 'regal' (I've seen this in another clue).
'served up' says the letters should be written in reverse (in a down clue, going upwards).
'regal' written backwards gives 'LAGER'.
'for a' is the link.
(Other definitions for lager that I've seen before include "Regal sort of beer" , "A brew" , "A regal sort of drink" , "The drink could be regal" , "Pilsner, for example" .)