To covet so unconscionably in an undertone (5,4)

I believe the answer is:

sotto voce

I'm a little stuck... Click here to teach me more about this clue!

'in an undertone' is the definition.
(I've seen this in another clue)

'to covet so unconscionably' is the wordplay.
'to covet so' anagrams to 'SOTTO VOCE'.
But, I am not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for sotto voce that I've seen before include "Spoken quietly" , "In an undertone, from Italian" , "on the quiet" , "Speaking quietly" , "In an undertone from Italy" .)

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

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