Drink fit for royalty served up (5)
I believe the answer is:
lager
'drink' is the definition.
(lager is a kind of drink)
'fit for royalty served up' is the wordplay.
'fit for royalty' becomes 'regal'.
'served up' says the letters should be written backwards.
'regal' written backwards gives 'LAGER'.
(Other definitions for lager that I've seen before include "Lout's drink?" , "Light-bodied beer" , "Pilsner, for example" , "Bottom-fermented beer" , "African camp" .)