Opposing court abandoning arrangement (6)
I believe the answer is:
contra
'abandoning arrangement' is the definition.
I can't tell whether this definition defines the answer.
'opposing court' is the wordplay.
'opposing' becomes 'con' (I've seen this in another clue).
'court' becomes 'tra' (I can't explain this - if you can you should give a lot more credence to this answer).
'con'+'tra'='CONTRA'
Can you help me to learn more?
(Other definitions for contra that I've seen before include "Rebel fighter" , "Against in argument" , "Revolutionary fighter" , "US-backed fighter" , "(One) opposed (to the Sandinistas)" .)