Effervescence (4)
'effervescence' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for fizz that I've seen before include "Bubbles in champagne?" , "Hissing sound; champagne" , "Effervesce" , "Froth" , "Gas in drink" .)
(Another definition for spritzig that I've seen is " sparkling wine".)