Reserved like gin in champagne! (6)
I believe the answer is:
silent
'reserved' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for silent that I've seen before include "Inaudible" , "Wordless" , "Taciturn" , "Dumb" , "Listen in order to be quiet" .)