The most common and most likely answer to this crossword clue is the 10 letter word TWENTY-ONE
I've seen this crossword clue in Independent
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More clues leading to the result TWENTY-ONE
Buddy explains!
The straight part
We know that "number" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case number = twenty-one.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 TWENTY-ONE mean?
TWENTY-ONE noun- Blackjack.
- A basketball-based game in which players attempt to score exactly twenty-one points.
- The cardinal number occurring after twenty and before twenty-two, represented in Roman numerals as XXI and in Arabic numerals as 21.