Radiolocation (5)
I believe the answer is:
radar
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">radiolocation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for radar that I've seen before include "Range-finding apparatus" , "Technique using beam" , "waves to expose foe" , "System of detection by echoes" , "location finder" .)