Underhanded tell-tale (5)
I believe the answer is:
sneak
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">underhanded tell-tale</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sneak that I've seen before include "thief" , "peach" , "Creep" , "Go furtively and tell tales" , "Telltale; furtive person" .)