Hinder or prevent (6)
I believe the answer is:
thwart
I believe this is a double definition.
'hinder' is the first definition.
(thesaurus)
'prevent' is the second definition.
(I know that thwart is a more specific form of the action prevent)
(Other definitions for thwart that I've seen before include "Prevent from accomplishing something" , "check" , "Stymie" , "Defeat" , "Oppose successfully" .)