Crossword Genius

Cross river shortly after two vessels (12)

Ross

I believe the answer is:

cantankerous

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'cross' is the definition.
(both can mean angry or bad-tempered)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for cantankerous that I've seen before include "Awkward" , "can be prickly, too!" , "Stubbornly obstructive" , "Bloody-minded -- non-UK car seat (anag)" , "like a wrangler" .)

I've seen this clue in The Telegraph.
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