Secret plotter (7)
I believe the answer is:
schemer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">secret plotter</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 schemer that I've seen before include "one inventing plots" , "Devious type" , "Plotter and planner" , "Machiavelli" , "Cunning planner" .)