Pity my matchless busy physical vessels protecting against infection (9,6)

I believe the answer is:

lymphatic system

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'physical vessels protecting against infection' is the definition.
I can't judge whether this definition defines the answer.

'pity my matchless busy' is the wordplay.
'busy' indicates anagramming the letters.
'pity'+'my'+'matchless'='pitymymatchless'
'pitymymatchless' with letters rearranged gives 'LYMPHATIC SYSTEM'.

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

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