Hinder, frustrate (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)
'frustrate' is the second definition.
(I've seen this in another clue)
(Other definitions for stymie that I've seen before include "Obstruction (originally at golf)" , "Block; hinder" , "balk" , "Situation from which it is almost impossible to proceed" , "Impede, say golf stroke" .)