Crossword Genius

Company doing volte-face in lively dance number (9)

Ross

I believe the answer is:

octillion

I'm a little stuck... Click here to teach me more about this clue!

'number' is the definition.
(I have seen 'Large number' mean 'octillion' so perhaps 'number' could also mean 'octillion')

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Another definition for octillion that I've seen is " Large number".)

I've seen this clue in The Independent.
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