With everything needed to create barrier (4)
I believe the answer is:
wall
'barrier' is the definition.
(thesaurus)
'with everything needed' is the wordplay.
'with' becomes 'w' (abbreviation).
'everything' becomes 'all' (I've seen this before).
'needed' means one lot of letters go next to another.
'w'+'all'='WALL'
'to create' acts as a link.
(Other definitions for wall that I've seen before include "Side of building/room" , "Room divider" , "Boundary of brick or stone" , "Built barrier" , "Brick/stone barrier" .)