Equestrian contest (5-3,5)
I believe the answer is:
three-day event
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">equestrian contest</span>' is the definition.<br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for three-day event that I've seen before include "Equestrian competition comprising several disciplines" , "Dressage, cross-country and showjumping" , "Equestrian competition involving several skills" , "Horse-riding competition" .)