Reportedly origin for dressing (5)

I believe the answer is:

sauce

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

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

(Other definitions for sauce that I've seen before include "Insolence" , "Flavourful relish" , "It's good for the goose and gander" , "Condiment - impertinence" , "''Hunger is good .....''" .)

I've seen this clue in The Guardian.

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