Quench, allay (5)
I believe the answer is:
slake
I believe this is a double definition.
'quench' is the first definition.
(synonyms)
'allay' is the second definition.
(synonyms)
(Other definitions for slake that I've seen before include "Assuage" , "Satisfy one's thirst" , "Quench (one's thirst)" .)