Rotten tongue? (3,8)

I believe the answer is:

bad language

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'rotten tongue?' is the definition.
The definition suggests a singular noun which matches the answer.

'rotten tongue?' is the wordplay.
'rotten' becomes 'bad' (similar in meaning).
'tongue?' becomes 'language' (tongue is a kind of language).
'bad'+'language'='BAD LANGUAGE'

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I've seen this clue in The Irish News.

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