Crossword Genius

Perform unprepared quote if speaking about promotion (5-4)

Ross

I believe the answer is:

sight-read

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'perform unprepared' is the definition.
(synonyms)

'quote if speaking about promotion' is the wordplay.
I cannot really understand how this works, but
'about' could be 'rea' (I've seen this in other clues) and 'rea' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Another definition for sight-read that I've seen is " Interpret music without preparation".)

I've seen this clue in The Times.
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