Invalidation (9)
I believe the answer is:
annulment
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">invalidation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that invalidation can be written as annulment)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for annulment that I've seen before include "Declaration of invalidity, of a marriage say" , "cancellation" , "Countermand" , "Invalidation" , "dissolution" .)