The most common and most likely answer to this crossword clue is the 9 letter word NOVOCAINE
N
O
V
O
C
A
I
N
E
More clues leading to the result NOVOCAINE
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 = novocaine.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 NOVOCAINE mean?
NOVOCAINE noun- Alternative letter-case form of Novocaine