Levels of nonsense drop off, alas, only at the end (9)

I believe the answer is:

bulldozes

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

'levels' is the definition.
(bulldozing is a kind of levelling)

'nonsense drop off alas only at the end' is the wordplay.
I cannot quite see how this works, but
'nonsense' could be 'bull' (I've seen this before) and 'bull' is present in the answer.
'drop off' could be 'doze' (I've seen this in another clue) and 'doze' is found in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

'of' is the link.

Can you help me to learn more?

I've seen this clue in The Times.

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