Equestrian discipline is habit coming with time (8)
I believe the answer is:
dressage
'equestrian discipline' is the definition.
(I've seen this before)
'habit coming with time' is the wordplay.
'habit coming' becomes 'dress' (I've seen this before. I am not sure about the 'coming' bit.).
'with' is a charade indicator (letters next to each other).
'time' becomes 'age' (age is a kind of time).
'dress'+'age'='DRESSAGE'
'is' is the link.
Can you help me to learn more?
(Other definitions for dressage that I've seen before include "Part of equestrian event" , "Equestrian performance" , "Horse-training" , "Method of horse training" , "Equestrian manoeuvres" .)