Eavesdropper (5)
I believe the answer is:
snoop
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">eavesdropper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for snoop that I've seen before include "Furtively investigate" , "Informally, pry inquisitively" , "Investigate; pry" , "-- Dogg, US rapper; spy" , "Furtively look around" .)