Northern track turning back around small glacial ridge (5)

I believe the answer is:

eskar

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'glacial ridge' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for eskar that I've seen before include "Gravelly ridge" , "ridge of gravel" .)

I've seen this clue in The Sunday Times and The Times.

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