Unfastened or removed a barrier (6)
I believe the answer is:
opened
'unfastened or removed a barrier' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for opened that I've seen before include "Undone, begun" , "Afforded access" , "unwrapped" , "Exposed to view" , "Gave access by unlocking" .)