Straddling is the most enjoyable time on the horse (8)
I believe the answer is:
bestride
'straddling is' is the definition.
I can't judge whether this definition defines the answer.
'most enjoyable time on the horse' is the wordplay.
'most enjoyable time' becomes 'bes' (I am not sure about this - if you are sure you should believe this answer much more).
'on' means one lot of letters go next to another.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'horse' becomes 'ride'.
'bes'+'t'+'ride'='BESTRIDE'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for bestride that I've seen before include "Sit or stand over something imposingly" , "Straddle" , "Mount" , "Mounted" , "Have a leg either side of" .)