Fizz with impatience, do they? (8)
I believe the answer is:
champers
'fizz' is the definition.
(both are informal terms for champagne)
I don't understand the remainder of the clue.
(Other definitions for champers that I've seen before include "People putting their teeth in" , "celebratory drink" , "Kind of sparkling wine (slang)" , "Bubbly" , "People who eat" .)