Discourage, dissuade (5)
I believe the answer is:
deter
This clue is a double definition.
'discourage' is the first definition.
(I know that discourage can be written as deter)
'dissuade' is the second definition.
(I know that dissuade can be written as deter)
(Other definitions for deter that I've seen before include "Hinder, prevent" , "Put off (from an action)" , "Inhibit" , "Cause not to do something" , "Daunt" .)