Happening by chance (10)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">happening by chance</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 accidental that I've seen before include "Happening by chance" , "without planning" , "not intended by composer?" , "change of key" , "Sign raising or lowering a musical note" .)
(Other definitions for contingent that I've seen before include "Depending (on) - part of military force" , "army unit" , "Company" , "Quota of troops" , "group of people" .)