Crossword Genius

Vessel or two (9,4)

Ross

I believe the answer is:

container ship

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'vessel' is the first definition.
(container ship is a kind of vessel)

'two' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

'or' is the link.

Can you help me to learn more?

(Other definitions for container ship that I've seen before include "Large cargo vessel" , "Vessel such as docks at Felixstowe" , "Large transport vessel" , "Large transporter" .)

I've seen this clue in The Guardian.
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