How many a crazy lady falls in love? (5)

I believe the answer is:

madly

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

'how many a crazy lady falls in love?' is the definition.
I can't tell whether this defines the answer.

'how many a crazy lady' is the wordplay.
'how many' becomes 'm' (Roman numeral for a thousand. I am not sure about the 'how' bit.).
'a crazy' is an anagram indicator.
'lady' with letters rearranged gives 'adly'.
'm'+'adly'='MADLY'

Can you help me to learn more?

(Another definition for madly that I've seen is " "Deeply truly ____"".)

I've seen this clue in The Globe and Mail.

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