Outer limits (5)
I believe the answer is:
edges
'outer limits' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for edges that I've seen before include "Borders, rims" , "Des, e.g. (anag.)" , "Outside limits" , "Sharpened sides of knives etc" , "Boundaries of a surface" .)