Complain to king about river (6)

I believe the answer is:

grouse

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

'complain' is the definition.
(grouse can mean to complain or grumble)

'king about river' is the wordplay.
'king' becomes 'GR' (short for Georgius Rex, King George in Latin).
'about river' becomes 'ouse' (Yorkshire river. I am not sure about the 'about' bit.).
'gr'+'ouse'='GROUSE'

'to' is the link.

Can you help me to learn more?

(Other definitions for grouse that I've seen before include "Bellyache" , "excellent in New Zealand" , "Complain like gamebird" , "1D [GAMEBIRD] < having grumble" , "No shooting it before 12 August" .)

I've seen this clue in The Mirror.

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.