Invalidates (6)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">invalidates</span>' is the definition.<br/ ><span class="explanation-format__explanation">('annul' can be a synonym of 'invalidate')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for annuls that I've seen before include "Renders boid" , "Cancels officially" , "Repeals or rescinds" , "Cancels, abolishes" , "Declares invalid" .)