Race over fences (12)
I believe the answer is:
steeplechase
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">race over fences</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for steeplechase that I've seen before include "Race over fences" , "Horse race with jumps and ditches" , "Running event over hurdles and water jumps" , "Type of horse race" , "Race with obstacles to be jumped" .)