Obstructing; hindering (8)
I believe the answer is:
impeding
I believe this clue is a double definition.
'obstructing' is the first definition.
('impede' can be a synonym of 'obstruct')
'hindering' is the second definition.
(I know that hindering can be written as impeding)
(Other definitions for impeding that I've seen before include "Preventing movement" , "Slowing down" , "Hindering" .)