Accident; disaster (6)
I believe the answer is:
mishap
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">accident</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(mishap is a kind of accident)</span><br/ ><br/ >'<span class="explanation-format__original">disaster</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for mishap that I've seen before include "An accident, piece of bad luck" , "Blow" , "Contretemps" , "Stroke of bad luck" , "Unlucky development" .)