The most common and most likely answer to this crossword clue is the 9 letter word MEDIATION
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More clues leading to the result MEDIATION
Buddy explains!

The straight part
We know that "Arbitration" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case arbitration = mediation.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does MEDIATION mean?
MEDIATION noun- Negotiation to resolve differences conducted by some impartial party.
- The act of intervening for the purpose of bringing about a settlement.