As the UK is now sovereign at last, time they leave the stage (6)
I believe the answer is:
exeunt
'they leave the stage' 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 exeunt that I've seen before include "They leave (stage direction)" , "More than one exit?" , "Stage direction (Latin, they go out)" , "Stage direction to a group of actors (Latin)" , "(Actors) leave stage" .)