Diminishing lute composition by head of performance (5)

I believe the answer is:

letup

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'diminishing lute composition by head of performance' is the definition.
I can't tell whether this definition defines the answer.

'lute composition by head of performance' is the wordplay.
'composition' is an anagram indicator (letters arranged or composed in a different order).
'by' means one lot of letters go next to another.
'head of' says to take the initial letters.
The initial letter of 'performance' is 'p'.
'lute' is an anagram of 'letu'.
'letu'+'p'='LETUP'

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(Another definition for letup that I've seen is " relief".)

I've seen this clue in The Daily Express.

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