Attendant serving drink to Queen (6)
I believe the answer is:
porter
'attendant' is the definition.
(attendant in a hotel)
'drink to queen' is the wordplay.
'drink' becomes 'port' (I've seen this before).
'to queen' becomes 'er' (abbreviation for Elizabeth Regina).
'port'+'er'='PORTER'
'serving' acts as a link.
(Other definitions for porter that I've seen before include "Doorkeeper; dark beer" , "Cole - - , songwriter" , "One carries luggage" , "Hotel luggage carrier" , "He should be able to carry" .)