Nice and sound after treatment, scarlet rash (12)

I believe the answer is:

unconsidered

'rash' is the definition.
(thesaurus)

'nice and sound after treatment scarlet' is the wordplay.
'and' says to put letters next to each other.
'after treatment' indicates an anagram.
'scarlet' becomes 'red' ('red' can be a synonym of 'scarlet').
'nice'+'sound'='nicesound'
'nicesound' is an anagram of 'unconside'.
'unconside'+'red'='UNCONSIDERED'

I've seen this clue in The Times.

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