Crossword Genius

Dirty residence half scrubbed up (4)

Ross

I believe the answer is:

lewd

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'dirty' is the definition.
(similar in meaning)

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

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(Other definitions for lewd that I've seen before include "Salacious" , "Sexually crude" , "Indecent, licentious" , "Obscene - lustful - sensual" , "Dirty" .)

I've seen this clue in The Guardian.
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