Funny, mirthful Noel, OK? (3-2-3-4)

I believe the answer is:

run-of-the-mill

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'ok?' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?

'funny mirthful noel' is the wordplay.
'funny' indicates anagramming the letters.
'mirthful'+'noel'='mirthfulnoel'
'mirthfulnoel' is an anagram of 'RUN-OF-THE-MILL'.

Can you help me to learn more?

(Other definitions for run-of-the-mill that I've seen before include "Everyday" , "Unexceptional" , "Mediocre" , "Ordinary" , "Bog standard" .)

I've seen this clue in The Everyman puzzle in The Observer.

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