Sat possibly on horse? (7)
I believe the answer is:
astride
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for astride that I've seen before include "With a leg on both sides" , "Passing across" , "Not side saddle" , "With one leg on either side, as sitting on horse" , "With legs stretched apart - tirades (anag)" .)