Rowing crew said to be in the river! (4)

I believe the answer is:

eyot

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

'river' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for eyot that I've seen before include "There's one at Chiswick" , "Small river island" , "land in the river" , "Fawlty Towers waiter" , "Islet found in a river, (especially in England)" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.