Please employ snuff! (5)
I believe the answer is:
douse
'snuff' is the definition.
(I've seen this before)
'please employ' is the wordplay.
'please' becomes 'do' (I've seen this in other clues).
'employ' becomes 'use' (synonyms).
'do'+'use'='DOUSE'
(Other definitions for douse that I've seen before include "Drench; extinguish" , "duck in water" , "Plunge into water" , "can make you really wet" , "Smother with water" .)