Sudden, unexpected (6)
I believe the answer is:
abrupt
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">sudden</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">unexpected</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for abrupt that I've seen before include "Unexpected -- precipitous" , "Offhand" , "Short in manner" , "Sudden, maybe discourteous" , "Brusque, curt" .)