Penalty -- poor United, missing one, made small adjustments (4-5)

I believe the answer is:

fine-tuned

'made small adjustments' is the definition.

'penalty poor united missing one' is the wordplay.
'penalty' becomes 'fine' (fine is a kind of penalty).
'poor' indicates an anagram.
'missing' is a deletion indicator.
'one' becomes 'i' (Roman numeral).
'united' with 'i' taken out is 'unted'.
'unted' is an anagram of 'tuned'.
'fine'+'tuned'='FINE-TUNED'

(Another definition for fine-tuned that I've seen is " Define nut (anag)".)

I've seen this clue in The Telegraph.

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