Miraculous nun is at God's disposal (10)

I believe the answer is:

astounding

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'miraculous' is the definition.
(thesaurus)

'nun is at god's disposal' is the wordplay.
'nun is at god' can be anagrammed to 'ASTOUNDING'.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for astounding that I've seen before include "Extraordinary" , "Stunning" , "Amazing" .)

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