Riding skill is habit that comes with time (8)
I believe the answer is:
dressage
'riding skill' is the definition.
(I've seen this before)
'habit that comes with time' is the wordplay.
'habit' becomes 'dress' (I've seen this before).
'that comes with' says to put letters next to each other.
'time' becomes 'age' (an age is a period of time).
'dress'+'age'='DRESSAGE'
'is' is the link.
(Other definitions for dressage that I've seen before include "Equestrian performance" , "Equestrian manoeuvres" , "Part of equestrian event" , "Olympic event" , "equestrian activity" .)