Make sharper (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">make sharper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(honing is a kind of making sharper)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for hone that I've seen before include "Sharpen tool on stone" , "Polish" , "Smooth stone" , "Strop" , "Sharpen (a blade)" .)