Splendid booze-up! (5)
I believe the answer is:
regal
'splendid' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for regal that I've seen before include "King-like" , "King's" , "Kingly or queenly" , "Befitting a monarch" , "Royal - lager (anag)" .)