River creature getting closer in Cockney’s game (5)

I believe the answer is:

otter

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

'river creature' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for otter that I've seen before include "Freshwater carnivorous mammal with webbed and clawed feet" , "Freshwater brown carnivore" , "river in Honiton" , "Tarka, for one" , "Something furry" .)

I've seen this clue in The Everyman puzzle in The Observer.

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.