TV studio sign (2,3)
I believe the answer is:
on air
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tv studio sign</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for on air that I've seen before include "Transmitting now!" , "Broadcasting live" , "Broadcasting studio sign" , "In the process of broadcasting on radio or TV" , "with audience?" .)