Sudden and unexpected (6)
I believe the answer is:
abrupt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sudden and unexpected</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for abrupt that I've seen before include "Sudden and unexpected" , "Short in manner" , "Hurried or curt" , "Short and brusque" , "Unexpected - terse" .)