Perkins or Lawley say to take legal action (3)

I believe the answer is:

sue

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'take legal action' 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 sue that I've seen before include "Litigate" , "Take proceedings against (a person)" , "Make a legal claim" , "Take legal action against (someone), girl's name" , "Use to prosecute" .)

I've seen this clue in The Telegraph.

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