After editing, tell Sun it's valueless (4,3)

I believe the answer is:

null set

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'it's valueless' is the definition.
I can't tell whether this defines the answer.

'after editing tell sun' is the wordplay.
'after editing' indicates anagramming the letters.
'tell'+'sun'='tellsun'
'tellsun' is an anagram of 'NULL SET'.

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I've seen this clue in The Guardian.

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