Small loudspeaker (7)
I believe the answer is:
tweeter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">small loudspeaker</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tweeter that I've seen before include "hi-fi unit?" , "One relaying notes" , "piece of hi-fi" , "part of speaker" , "one delivering a short message?" .)