Half-tamed horse (6)
I believe the answer is:
bronco
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">half-tamed horse</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bronco that I've seen before include "An unbroken mustang, bucking perhaps" , "Wild horse of the West" , "Wild bucking horse" , "Half-tamed horse used in rodeos" , "Wild horse of W. US" .)