Speech indistinct — language muffled (5)

I believe the answer is:

hindi

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'muffled' is the definition.
Although both the answer and definition are adjectives, I don't see how one could define the other.

'speech indistinct language' is the wordplay.
'HINDI' is hidden in amongst the letters.
But, I am uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for hindi that I've seen before include "An official language of India" , "One of India's official languages" , "It's spoken abroad" , "Indian language" , "Ind. Language" .)

I've seen this clue in The Times.

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