OAP leads conga, having worked out musical instruction (2,4,2,5)

I believe the answer is:

da capo al segno

'musical instruction' is the definition.

'oap leads conga having worked out' is the wordplay.
'having worked out' indicates an anagram.
'oap'+'leads'+'conga'='oapleadsconga'
'oapleadsconga' is an anagram of 'DA CAPO AL SEGNO'.

I've seen this clue in The Guardian.

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