Courage sometimes needed on the road (4)

I believe the answer is:

grit

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'courage' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for grit that I've seen before include "Jock's enormous" , "Small hard particles - courage" , "Small hard particles - determination" , "Persevering courage" , "Coarse stone or sand" .)

I've seen this clue in the Evening Standard.

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