Revolver inventor (4)
I believe the answer is:
colt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">revolver inventor</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for colt that I've seen before include "pistol" , "Youngster" , "Mount" , "firearm" , "Handgun -- young horse" .)