Hinder, thwart (6)
I believe the answer is:
stymie
I believe this clue is a double definition.
'hinder' is the first definition.
(I know that hinder can be written as stymie)
'thwart' is the second definition.
(I've seen this before)
(Other definitions for stymie that I've seen before include "Block or thwart, say a golf putt" , "Block or thwart an activity" , "Thwart -- my ties (anag)" , "Block or thwart, perhaps on putting green" , "Block or obstruct as in golf (6)" .)