Peeping Tom (6)
I believe the answer is:
voyeur
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">peeping tom</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for voyeur that I've seen before include "One who spies on others for sexual gratification" , "A secret spectator, perhaps for sexual gratification" , "A secret spectator, often in sexual situation" , "One who derives pleasure from watching others" , "One who watches" .)