Exchange or swap (6)
I believe the answer is:
switch
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">exchange</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that exchange can be written as switch)</span><br/ ><br/ >'<span class="explanation-format__original">swap</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that swap can be written as switch)</span><br/ ><br/ ></span>
(Other definitions for switch that I've seen before include "turn" , "Device for changing electrical connections" , "Change or exchange" , "Change round" , "Device for opening or closing a circuit" .)