Crossword Genius

River carp sandwiches put away (5,4)

Ross

I believe the answer is:

great ouse

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

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

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for great ouse that I've seen before include "Flower" , "Fens river" .)

I've seen this clue in The Independent.
Want a hint initially instead of a full solution? Install my app