Sudden (6)
I believe the answer is:
abrupt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sudden</span>' is the definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for abrupt that I've seen before include "Offhand" , "Short, sharp or sudden" , "Sudden; hasty, curt" , "Sudden; precipitous" , "Short and brusque" .)