Part of a bridle (3)
I believe the answer is:
bit
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">part of a bridle</span>' is the definition.<br/ ><span class="explanation-format__explanation">('bit' is part of 'bridle')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bit that I've seen before include "Cutting head of a drill" , "gripped" , "Morsel" , "Took effect - fragment" , "scrap" .)