Down-to-earth Ms Stubbs fixed leader's criminal defect (10)

I believe the answer is:

unaffected

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'down-to-earth ms stubbs fixed leader's criminal defect' is the definition.
I can't tell whether this definition defines the answer.

'stubbs fixed leader's criminal defect' is the wordplay.
'stubbs' becomes 'Una' (actress Una Stubbs is an example).
'leader's' suggests taking the first letters (I've seen 'leader' mean this).
'criminal' indicates anagramming the letters.
The initial letter of 'fixed' is 'f'.
'defect' is an anagram of 'fected'.
'una'+'f'+'fected'='UNAFFECTED'

Can you help me to learn more?

(Another definition for unaffected that I've seen is " Sincere, genuine".)

I've seen this clue in The Guardian.

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