Many of our menus must be updated (8)

I believe the answer is:

numerous

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

'many' is the definition.
(similar in meaning)

'our menus must be updated' is the wordplay.
'our menus' anagrams to 'NUMEROUS'.
However, I am unsure how this is indicated.

'of' is the link.

Can you help me to learn more?

(Other definitions for numerous that I've seen before include "Goodly but indefinite number" , "Amounting to a large indefinite number" , "Umpteen" , "Ever so many" , "Consisting of a large but indefinite number" .)

I've seen this clue in The Sunday Times.

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