Bird loses part in crest (5)

I believe the answer is:

ridge

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

I don't understand the rest of the clue.

(Other definitions for ridge that I've seen before include "Raised strip of land" , "Raised strip between two furrows" , "Peak" , "Part of mountain" , "Long narrow natural elevation" .)

I've seen this clue in The Sun.

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