Hedge set around borders (5)
I believe the answer is:
edges
'borders' is the definition.
('edge' can be a synonym of 'border')
'hedge set around' is the wordplay.
'around' indicates a hidden word.
'EDGES' is hidden within 'hedge set'.
(Other definitions for edges that I've seen before include "They're used for cutting" , "Outer limits" , "Slowly moves" , "Boundaries of a surface" , "Borders, rims" .)