Number, by third of voyage on fated ship, joined number? (9)

I believe the answer is:

novocaine

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'number' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

I can't explain the remainder of the clue.

Can you help me to learn more?

(Another definition for novocaine that I've seen is " anaesthetic".)

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

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