Cancel, make void (5)
I believe the answer is:
annul
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">cancel</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(annulling is a kind of cancelling)</span><br/ ><br/ >'<span class="explanation-format__original">make void</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for annul that I've seen before include "Cancel officially" , "Scrap" , "Countermand" , "Make invalid" , "Obligation" .)