Choosing one from about fifty performing (8)

I believe the answer is:

singling

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'choosing one' is the definition.
I can't tell whether this definition defines the answer.

'about fifty performing' is the wordplay.
'about' means one lot of letters goes inside another.
'fifty' becomes 'l' (Roman numeral).
'performing' becomes 'singing'.
'l' placed within 'singing' is 'SINGLING'.

'from' acts as a link.

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I've seen this clue in the Evening Standard.

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