Crossword Genius

Infected flier's declaration was unlawful (7)

Ross

I believe the answer is:

illegal

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'unlawful' is the definition.
(associated in meaning)

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

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(Other definitions for illegal that I've seen before include "Black-market" , "Contraband" , "Not in conformity with law" , "Not allowed" , "Criminal, illicit" .)

I've seen this clue in the Sydney Morning Herald.
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