Barber's obstacle (3)
I believe the answer is:
ear
'barber's obstacle' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ear that I've seen before include "willingness to listen" , "one hears" , "Appreciation of sounds" , "Spike of, eg, corn" , "'Give every man thine ..., but few thy voice'/Hamlet" .)