Hand in notice (6)
I believe the answer is:
resign
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hand in notice</span>' is the definition.<br/ ><span class="explanation-format__explanation">(to hand in one's notice is to resign)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for resign that I've seen before include "surrender" , "Turn over" , "Give up position" , "Quit" , "admit defeat" .)