Drill part (3)
I believe the answer is:
bit
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">drill part</span>' is the definition.<br/ ><span class="explanation-format__explanation">('bit' is part of 'drill')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for bit that I've seen before include "Between horse's teeth, this loses control" , "Cutting head of a drill" , "Piece; horse's restraint" , "scrap" , "Small piece - used teeth" .)