More mouth-watering (7)
I believe the answer is:
tastier
'more mouth-watering' is the definition.
('tasty' can be a synonym of 'mouth-watering')
This is all the clue.
(Other definitions for tastier that I've seen before include "Having a more pleasant flavour" , "More attractive" , "More flavoursome" , "More palatable" , "More appetising" .)