Mute very Republican old lizard (7)

I believe the answer is:

sordino

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'mute' is the definition.
(thesaurus)

'very republican old lizard' is the wordplay.
'very' becomes 'so' (both can mean 'extremely').
'republican' becomes 'R' (political abbreviation).
'old lizard' becomes 'dino' (I can't justify this - if you can you should believe this answer much more).
'so'+'r'+'dino'='SORDINO'

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