Presenter nearly beside Ms Giedroyc lay vacuously down (10)

I believe the answer is:

melancholy

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'down' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

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(Other definitions for melancholy that I've seen before include "Low spirits" , "[ODE] subject" , "Cheerless" , "Sad - tendency to depression" , "Gloomy, sad" .)

I've seen this clue in The Telegraph.

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