Obstruct from behind, erroneously (6)
I believe the answer is:
hinder
'obstruct' is the definition.
('hinder' can be a synonym of 'obstruct')
'from behind erroneously' is the wordplay.
'from' indicates the answer is hidden within the clue.
'HINDER' is hidden within 'behind erroneously'.
(Other definitions for hinder that I've seen before include "Keep back by delaying progress" , "Obstruct or hold back" , "Delay progress, obstruct" , "Obstruct, impede" , "Impede, keep back" .)