Make numb (6)
I believe the answer is:
deaden
'make numb' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for deaden that I've seen before include "Make weaker or quieter" , "Take life" , "Make numb, deprive of feeling" , "Muffle impact" , "Muffle, deprive of feeling" .)