Crossword Genius

Tried working without energy or grime (4)

Ross

I think it could be either:

dust

dirt
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'grime' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

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(Other definitions for dust that I've seen before include "Powdered matter" , "Tiny particles of dirt, skin flakes etc" , "Powdery dirt in dry areas" , "Stud (anag)" , "Sprinkle -- powder" .)

I've seen this clue in The Mirror.
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