Rude grinners stupidly waving a white flag? (12)

I believe the answer is:

surrendering

'waving a white flag?' is the definition.
(to wave a white flag is to surrender)

'rude grinners stupidly' is the wordplay.
'stupidly' indicates anagramming the letters (a stupid ordering of the letters).
'rude'+'grinners'='rudegrinners'
'rudegrinners' with letters rearranged gives 'SURRENDERING'.

(Another definition for surrendering that I've seen is " Giving up".)

I've seen this clue in The Times.

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.