I arrive on schedule, you texted and improvised (9)

I believe the answer is:

impromptu

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'improvised' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for impromptu that I've seen before include "Without much planning" , "On the spur of the moment" , "unrehearsed piece" , "Without pre-planning" , "Spontaneous" .)

I've seen this clue in The Independent.

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