Horse that's ridden at the peak (5)
I believe the answer is:
mount
'the peak' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for mount that I've seen before include "Climb - eg Everest" , "Climb, stairs say" , "seat" , "Increase" , "Fix onto a backing" .)