Crossword Genius

Blue feature of a feather-eater (4,2,3,5)

Ross

I believe the answer is:

down in the mouth

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

I cannot understand how the remainder of the clue works.

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(Other definitions for down in the mouth that I've seen before include "consequence of eating unprepared duck?" , "then spitting feathers?" , "evidence of poor pheasant plucking?" , "Hangdog" , "characteristic of a retriever on a duck hunt?" .)

I've seen this clue in the Sydney Morning Herald.
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