Scare off
I believe the answer is:
deter
'scare off' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for deter that I've seen before include "Hinder, prevent" , "Frighten off; prevent" , "Discourage through fear of consequences" , "Dishearten" , "Discourage (someone from an action)" .)