Quell (6)
I believe the answer is:
subdue
'quell' is the definition.
(I know that quell is a kind of subdue)
This is the entire clue.
(Other definitions for subdue that I've seen before include "Put down - quieten" , "Vanquish" , "Overcome, force to yield" , "Force to yield, tame" , "Bring under control, tame" .)