A wireless (5)
I believe the answer is:
radio
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a wireless</span>' is the definition.<br/ ><span class="explanation-format__explanation">('radio' can be a synonym of 'wireless')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for radio that I've seen before include "Electronic medium of communication" , "Receiving device" , "means of communication" , "send a message" , "Communications receiver" .)