Trophy competed for once lad's done with rap music (8,3)

I believe the answer is:

admirals cup

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'trophy competed for' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'lad's done with rap music' is the wordplay.
'done with' indicates anagramming the letters.
'rap'+'music'='rapmusic'
'lad' anagrammed with 'rapmusic' gives 'ADMIRALS CUP'.

'once' is the link.

Can you help me to learn more?

(Another definition for admirals cup that I've seen is " yachting event".)

I've seen this clue in The Times.

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