Sheer quality of Sunshine Soap ad being broadcast (14)

I believe the answer is:

diaphanousness

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'sheer quality' is the definition.
The definition suggests a singular noun which matches the answer.

'sunshine soap ad being broadcast' is the wordplay.
'being broadcast' is an anagram indicator (letters scattered or cast around).
'sunshine'+'soap'+'ad'='sunshinesoapad'
'sunshinesoapad' is an anagram of 'DIAPHANOUSNESS'.

'of' acts as a link.

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I've seen this clue in The Times.

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