The most common and most likely answer to this crossword clue is the 8 letter word THIRTEEN
I've seen this crossword clue in The Guardian
T
H
I
R
T
E
E
N
More clues leading to the result THIRTEEN
- The unknown number holding weird rite as number of ill omen?
- Frenzied rite thus engulfs ill-omened figure
- Finally bet on neither odd number
- Prime time dancing therein?
- Hit enter randomly to get something in the first cell here?
- Cardinal in there crippled after tango
- Thin tree chopped up, a number being bad
- Ill-fated figure suffering therein, with temperature on the high side
- Coven, perhaps, subsequently holding ghastly rite
- In Tunisia, supply either 10 of 26
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 = thirteen.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 THIRTEEN mean?
THIRTEEN numeral- The cardinal number occurring after twelve and before fourteen, represented in Roman numerals as XIII and in Arabic numerals as 13.