Illegal scheme that's used in court (6)
I believe the answer is:
racket
This could be a double definition.
'illegal scheme' is the first definition.
(I've seen this before)
'used in court' is the second definition.
'racket' can be an answer for 'court' (thesaurus). I'm not sure about the 'used in' bit.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for racket that I've seen before include "Lot of noise or bat for game (6)" , "Din - strung bat" , "See 1" , "Unpleasant din" , "Light bat" .)