High-pitched signal (5)
I believe the answer is:
bleep
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">high-pitched signal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bleep that I've seen before include "Electronic alarm sound" , "Noise of alarm" , "Swearing substitute" , "High-pitched electrical signal" , "(Alarm) pulse" .)