They say ale density correlates to facial hair (5)

I believe the answer is:

beard

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'facial hair' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for beard that I've seen before include "Hair on the chin" , "Whiskers" , "Vandyke, perhaps" , "Oppose with effrontery" , "Facial growth" .)

I've seen this clue in The Irish Times.

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