Isotope has decayed in climactic moment (10)

I believe the answer is:

apotheosis

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'moment' is the definition.
(I have seen 'crowning moment' mean 'apotheosis' so perhaps 'moment' could also mean 'apotheosis')

'isotope has decayed in climactic' is the wordplay.
'isotope has' anagrams to 'APOTHEOSIS'.
Though, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for apotheosis that I've seen before include "Crowning point" , "Elevation to divine status" , "ideal" , "Deification" , "crowning moment" .)

I've seen this clue in The Telegraph.

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