Curt; sudden (6)
I believe the answer is:
abrupt
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">curt</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(both can mean rudely brief)</span><br/ ><br/ >'<span class="explanation-format__original">sudden</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ ></span>
(Other definitions for abrupt that I've seen before include "Rough and quick" , "Curt, sharp" , "Unexpected -- precipitous" , "Offhand" , "Impolite" .)