Dirty rotter on about a dog (4,6)

I believe the answer is:

blue heeler

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'a dog' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'dirty rotter on about' is the wordplay.
'dirty' becomes 'blue' (blue can mean pornographic).
'rotter' becomes 'heel' (I've seen this in another clue).
'on' becomes 're' (regarding).
'about' says the letters should be written in reverse.
're' written backwards gives 'er'.
'blue'+'heel'+'er'='BLUE HEELER'

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I've seen this clue in the Sydney Morning Herald.

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