Margins, borders (5)
I believe the answer is:
edges
This clue is a double definition.
'margins' is the first definition.
('edge' can be a synonym of 'margin')
'borders' is the second definition.
(an edge is a border or margin)
(Other definitions for edges that I've seen before include "They're farthest from the middle" , "Sharpened sides of blades" , "Margins" , "Des, e.g. (anag.)" , "Bounds" .)