Having filled to the brim, flew round (7)
I believe the answer is:
stopped
'flew round' is the definition.
The answer and definition can be both related to change as well as being past participle verbs.
Perhaps there's an association between them I don't understand?
'having filled to the brim' is the wordplay.
I cannot really see how this works, but
'to' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stopped that I've seen before include "Prevented" , "What Terminator did" , "Ceased, ended" , "gave up" .)