Sit there, refusing to commit, which creates a barrier (5)
I believe the answer is:
fence
'barrier' is the definition.
(fence is a kind of barrier)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for fence that I've seen before include "feature in horse-racing?" , "crook" , "Thief's dealer" , "Bound over this" , "railings" .)