Crossword Genius

First killer said to be crook (4)

Ross

I believe the answer is:

cane

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'to be crook' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for cane that I've seen before include "Strong, flexible stem" , "Eg, bamboo; punish" , "Stick; thrash" , "Beat - bamboo - stick" , "Malacca, perhaps" .)

I've seen this clue in The Sun.
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