Get a new barrier (4)
I believe the answer is:
gate
'barrier' is the definition.
(gate is a kind of barrier)
'get a new' is the wordplay.
'new' indicates anagramming the letters.
'get'+'a'='geta'
'geta' with letters rearranged gives 'GATE'.
(Other definitions for gate that I've seen before include "Box office take" , "Means of entry" , "Portal" , "Attendance figure" , "Facility in airport" .)