Figure lacking a horse (5)
I believe the answer is:
mount
'horse' is the definition.
(I know that mount is a type of horse)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for mount that I've seen before include "Steed" , "put on launch" , "hill" , "Get on - horse" , "- - Sinai" .)