What's white and sparkling as teeth? (8)
I believe the answer is:
champers
I believe this is a double definition.
'what's white and sparkling' is the first definition.
(informal term for champagne)
'teeth?' is the second definition.
(to champ can mean to bite)
'as' acts as a link.
(Other definitions for champers that I've seen before include "Drink casually" , "Kind of sparkling wine (slang)" , "People who eat" , "something sparkling!" , "Bubbly" .)