New dog, duller barking sound (4-8)

I believe the answer is:

well-grounded

'sound' is the definition.
(synonyms)

'new dog duller barking' is the wordplay.
'barking' is an anagram indicator (UK slang for mad).
'new'+'dog'+'duller'='newdogduller'
'newdogduller' anagrammed gives 'WELL-GROUNDED'.

I've seen this clue in The Telegraph.

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