Local talk in citadel unintelligible (7)

I believe the answer is:

dialect

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'local' is the definition.
(thesaurus)

'talk in citadel unintelligible' is the wordplay.
'citadel' can be anagrammed to 'DIALECT'.
But, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for dialect that I've seen before include "Regional version of a language" , "Patois" , "Local speech variant" , "Local way of speaking" , "Material damage" .)

I've seen this clue in The Sun.

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