The most common and most likely answer to this crossword clue is the 10 letter word BARGAINING
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More clues leading to the result BARGAINING
Buddy explains!

The straight part
We know that "negotiation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case negotiation = bargaining.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 BARGAINING mean?
BARGAINING verb- To make a bargain; to make a deal or contract for the exchange of property or services; to negotiate
- To transfer for a consideration; to barter; to trade
- The act of one who bargains.