He uses a sword but creates barriers (6)
I believe the answer is:
fencer
'he uses a sword but creates barriers' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for fencer that I've seen before include "His sport is swordplay" , "Swordsman" , "A sportsman with swords" , "who may intervene to keep neighbours apart?" , "Maker of barriers; user of foil" .)