Crossword Genius

In a monotone, starts to lecture youth lifting tyre (6)

Ross

I believe the answer is:

flatly

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

'in a monotone' is the definition.
I can't tell whether this definition defines the answer.

'starts to lecture youth lifting tyre' is the wordplay.
'starts to' indicates taking the first letters.
'lifting' is a charade indicator (letters next to each other).
'tyre' becomes 'flat' (flat is a kind of tyre).
The initial letters of 'lecture youth' is 'ly'.
'ly' put after 'flat' is 'FLATLY'.

Can you help me to learn more?

(Other definitions for flatly that I've seen before include "Absolutely" , "Categorically" , "in no uncertain manner" , "(Deny) without qualification" , "in uninspiring fashion" .)

I've seen this clue in The Times.
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