One's not prepared for these remarks (2-4)

I believe the answer is:

ad-libs

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'these remarks' is the definition.
(I have seen 'Extemporaneous remarks' mean 'ad-libs' so perhaps 'remarks' could also mean 'ad-libs')

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for ad-libs that I've seen before include "Extemporary remarks" , "Improvises" , "Extemporaneous remarks" .)

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