Crossword Genius

Crooked pair of girls, Parisian one taking the lead (7)

Ross

I believe the answer is:

illegal

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

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for illegal that I've seen before include "murder sure is!" , "Felonious" , "Contrary to law" , "Prohibited by law" , "Unauthorised" .)

I've seen this clue in The Independent.
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