No stranger to being sued (4)

I believe the answer is:
used
'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' is the 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" .)
