That's the end of the fox! (5)
I believe the answer is:
brush
'fox' is the definition.
The answer and definition can be both related to change as well as being verbs in their base form.
Perhaps you can see a link between them that I can't see?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for brush that I've seen before include "Tool for cleaning or painting" , "Sweep" , "Cleaning implement" , "Undergrowth, fox tail" , "Slight touch; fox's tail" .)