Slake (6)
I believe the answer is:
quench
'slake' is the definition.
(I know that slake can be written as quench)
This is the entire clue.
(Other definitions for quench that I've seen before include "Extinguish (a fire)" , "End a thirst" , "Satisfy thirst by drinking, or extinguish with water" , "Damp down" , "Slake - assuage" .)