Dissuade (5)
I believe the answer is:
deter
'dissuade' is the definition.
(I know that dissuade can be written as deter)
This is all the clue.
(Other definitions for deter that I've seen before include "Discourage or prevent from doing something" , "Cause not to do something" , "Try to prevent" , "Discourage (someone from an action)" , "stop" .)