Unlucky accident (6)
I believe the answer is:
mishap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unlucky accident</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mishap that I've seen before include "Accident, unlucky happening" , "Unpleasant accident" , "Accident, something going wrong" , "An accident or unlucky event" , "'Bad luck, mischance (6)'" .)