Clothing appearing on time for equestrian sport (8)
I believe the answer is:
dressage
'for equestrian sport' is the definition.
(dressage is a kind of equestrian sport)
'clothing appearing on time' is the wordplay.
'clothing' becomes 'dress' (dress is a kind of clothing).
'appearing on' says to put letters next to each other.
'time' becomes 'age' (an age is a period of time).
'dress'+'age'='DRESSAGE'
(Other definitions for dressage that I've seen before include "Method of training horses to do manoeuvres" , "Equestrian performance" , "Olympic event" , "The training of a horse in manoeuvres" , "Method of horse training" .)