Young male horse (4)
I believe the answer is:
colt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">young male 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 colt that I've seen before include "with a hefty kick?" , "pistol" , "Type of revolver and a young horse" , "Young male horse or cowboy revolver" , "Youngster" .)