Snack as two Italian rivers rise (no falls) (7)
I believe the answer is:
rarebit
'snack' is the definition.
(I've seen this before)
'two italian rivers rise no falls' is the wordplay.
I cannot really see how this works, but
'italian' could be 'it' and 'it' is found in the answer.
This explanation may well be incorrect...
'as' is the link.
(Other definitions for rarebit that I've seen before include "Melted cheese on hot toast" , "Cheesy snack" , "Cooked cheese on toast" , "Arbiter of tasty Welsh dish of cheese on toast" , "Welsh snack" .)