Swordsman who puts up a barrier (6)
I believe the answer is:
fencer
This clue is a double definition.
'swordsman' is the first definition.
(fencers use swords)
'who puts up a barrier' is the second definition.
(someone who puts up fences)
(Other definitions for fencer that I've seen before include "Sporty type" , "A sword sportsman" , "He sports with the sword" , "fighting sportsman" , "could be making enclosures" .)