Not sparkling, yet (5)
I believe the answer is:
still
I believe this is a double definition.
'not sparkling' is the first definition.
('still' is the opposite to 'sparkling')
'yet' is the second definition.
('still' can be a synonym of 'yet')
(Other definitions for still that I've seen before include "Stationary" , "Motionless, inactive" , "It's not effervescing" , "source of spirits" , "not bubbly" .)