River creature seen on Wimbledon common? (7)

I believe the answer is:

orinoco

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

'river' is the definition.
(Orinoco is an example)

I don't understand the rest of the clue.

(Other definitions for orinoco that I've seen before include "banker" , "South American river - lazy Womble" , "Great river in the north of S America, flows through Venezuela" , "O, I croon about the river" , "Womble; S. Amer. river" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app