Serve up a drink fit for a king (5)
I believe the answer is:
regal
'fit for a king' is the definition.
(I've seen this before)
'serve up a drink' is the wordplay.
'serve up' says the letters should be written backwards.
'a drink' becomes 'lager' (lager is a kind of drink).
'lager' back-to-front is 'REGAL'.
(Other definitions for regal that I've seen before include "King's" , "Befitting a monarch" , "Like a queen?" , "King-like" , "Grand and imposing" .)