To all appearances boy listens properly (10)

I believe the answer is:

ostensibly

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'to all appearances' is the definition.
(thesaurus)

'boy listens properly' is the wordplay.
'boy listens' can be anagrammed to 'OSTENSIBLY'.
But, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for ostensibly that I've seen before include "Seemingly" , "to all intents and purposes" , "Evidently" , "on the face of it" .)

I've seen this clue in the Sydney Morning Herald.

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