Wife finds everything a barrier (4)
I believe the answer is:
wall
'a barrier' is the definition.
(a wall acts as a barrier)
'wife finds everything' is the wordplay.
'wife' becomes 'w' (abbreviation).
'finds' says to put letters next to each other.
'everything' becomes 'all' (all things).
'w'+'all'='WALL'
(Other definitions for wall that I've seen before include "Barrier, internal or external" , "Barrier - side of room" , "Built barrier" , "Side of building" , "Dividing or protecting structure" .)