Carbonated water from Kiso Dam (4)
I believe the answer is:
soda
'carbonated water' is the definition.
(I've seen this before)
'from kiso dam' is the wordplay.
'from' indicates a hidden word.
'SODA' is hidden in the letters of 'kiso dam'.
(Other definitions for soda that I've seen before include "pressurised liquid" , "fizz" , "Whisky mixer" , "Variety of pop" , "Accompaniment to whisky" .)