Confirmed landlubber dies at sea (9)

I believe the answer is:

notarised

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'confirmed' is the definition.
('confirmed'->'notarized' is in my internal thesaurus and 'ize'->'ise')

'landlubber dies at sea' is the wordplay.
I cannot really see how this works, but
an anagram of 'dies' is 'ised' which is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Another definition for notarised that I've seen is " Authenticated".)

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