The most common and most likely answer to this crossword clue is the 8 letter word NEIGHING
I've seen this crossword clue in Financial Times
N
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G
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Buddy explains!

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 NEIGHING mean?
NEIGHING verb- (of a horse) To make its cry.
- To make a sound similar to a horse's cry.
- To scoff or sneer.
- The sound made by a horse; an act or instance of the verb neigh.