The most common and most likely answer to this crossword clue is the 9 letter word BROKERING
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The straight part
We know that "Negotiating" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case negotiating = brokering.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 BROKERING mean?
BROKERING verb- To act as a broker; to mediate in a sale or transaction.
- To act as a broker in; to arrange or negotiate.
- The act of one who brokers; mediation.