Season the water (6)
I believe the answer is:
spring
I believe this is a double definition.
'season' is the first definition.
(spring is a kind of season)
'the water' is the second definition.
(spring water is a kind of water)
(Other definitions for spring that I've seen before include "early in the year" , "Pounce -- pogo stick part" , "Shoot forth" , "The vernal season" , "Mechanical device" .)