Isn't informally tuned another way outside, so not contaminated (9)

I believe the answer is:

untainted

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'isn't informally tuned another way outside' is the definition.
I can't judge whether this defines the answer.

'not contaminated' is the wordplay.
'not' becomes 'un' (prefix meaning 'not').
'contaminated' becomes 'tainted' (tainting is a kind of contaminating).
'un'+'tainted'='UNTAINTED'

'so' is the link.

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(Other definitions for untainted that I've seen before include "Not polluted" , "without unwanted substances" , "Virginal" .)

I've seen this clue in The Daily Express.

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