Obstacles (8)
I believe the answer is:
barriers
'obstacles' is the definition.
(barrier is a kind of obstacle)
This is all the clue.
(Other definitions for barriers that I've seen before include "Obstacles designed to prevent advance or progress" , "Constructions that prevent or impede advance" , "Objects erected to control progress or access as by crowds" , "Obstructions" , "They're put up to block or protect" .)