Cliff sometimes left by accident (4)

I believe the answer is:

scar

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

I can't explain the rest of the clue.

(Other definitions for scar that I've seen before include "One left after having wound" , "Mark left by injury" , "Identifying mark" , "Mark of a wound remaining on the skin" , "Blemish - cicatrix" .)

I've seen this clue in The Globe and Mail.

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