Really happy, nun once idol destroyed (2,5,4)

I believe the answer is:

on cloud nine

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'really happy' is the definition.
'on cloud nine' can be an answer for 'happy' (I've seen this in another clue). I am not certain of the 'really' bit.

'nun once idol destroyed' is the wordplay.
'destroyed' indicates anagramming the letters.
'nun'+'once'+'idol'='nunonceidol'
'nunonceidol' anagrammed gives 'ON CLOUD NINE'.

Can you help me to learn more?

(Other definitions for on cloud nine that I've seen before include "Extremely happy" , "Elated" , "delighted" , "Ecstatic" , "Euphoric" .)

I've seen this clue in The Telegraph.

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