Hinder, obstruct (6)
I believe the answer is:
impede
I believe this clue is a double definition.
'hinder' is the first definition.
(I know that impede is a kind of hinder)
'obstruct' is the second definition.
(I know that obstruct is a kind of impede)
(Other definitions for impede that I've seen before include "Cramp" , "Delay; block progress of" , "Delay or obstruct" , "Hamper" , "check" .)