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

The straight part
We know that "of best quality" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case of best quality = top-notch.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 TOP-NOTCH mean?
TOP-NOTCH adjective- Very good; of the highest level or quality.