Smother, suppress (6)
I believe the answer is:
stifle
This clue is a double definition.
'smother' is the first definition.
(I know that smother can be written as stifle)
'suppress' is the second definition.
(I know that stifle is a more specific form of suppress)
(Other definitions for stifle that I've seen before include "Curb" , "Gag" , "Joint in hind leg of horse" , "Silence" , "Smother, suffocate" .)