Wireless (5)
I believe the answer is:
radio
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wireless</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for radio that I've seen before include "Communications medium" , "Sound broadcasting" , "Communicate with" , "MW, LW or FM sound source" , "Receiving apparatus" .)