No stranger to being sued? (4)

I believe the answer is:

used

I'm a little stuck... Click here to teach me more about this clue!

'no stranger' is the definition.
(I've seen this before)

'being sued' is the wordplay.
'sued' can be anagrammed to 'USED'.
But, I am not clear how the anagram is indicated.

'to' acts as a link.

Can you help me to learn more?

(Other definitions for used that I've seen before include "Scottish expert" , "Subject to exploitation" , "Brought into play" , "not got directly" , "Hand-me-down" .)

I've seen this clue in the Evening Standard.

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