Rival outlet collapsed — it's not to be seen (11)

I believe the answer is:

ultraviolet

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'not to be seen' is the definition.
I can't tell whether this defines the answer.

'rival outlet collapsed' is the wordplay.
'collapsed' indicates anagramming the letters.
'rival'+'outlet'='rivaloutlet'
'rivaloutlet' is an anagram of 'ULTRAVIOLET'.

'it's' is the link.

Can you help me to learn more?

(Other definitions for ultraviolet that I've seen before include "light range" , "Type of radiation" , "electromagnetic radiation" , "UV in full" , "form of invisible radiation" .)

I've seen this clue in The Guardian.

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