Write (or leave) quickly (4,3)
I believe the answer is:
dash off
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">write</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that dash off is a type of write)</span><br/ ><br/ >'<span class="explanation-format__original">leave quickly</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Another definition for dash off that I've seen is " Rush away".)