Notice China supporting British in court action (9)
I believe the answer is:
badminton
'court action' is the definition.
(I've seen this before)
'notice china supporting british' is the wordplay.
'notice' becomes 'ad' (short for advert).
'china' becomes 'minton' (I can't explain this - if you can you should give a lot more credence to this answer).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'ad'+'minton'='adminton'
'adminton' after 'b' is 'BADMINTON'.
'in' is the link.
Can you help me to learn more?
(Other definitions for badminton that I've seen before include "A sport; Beaufort seat" , "in which rackets are involved" , "Game played with a shuttlecock" , "Game using shuttlecock" , "One sport" .)