Outer border (3)
(Other definitions for rim that I've seen before include "Edge, border" , "'Brim, lip (3)'" , "Circular outer edge" , "Raised edge of a round object" , "Curved edge" .)
'outer border' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for edge that I've seen before include "Side, brink" , "Rim - move gradually" , "incisiveness" , "Bind" , "Outer limit" .)