Clandestine or deceptive (9)
I believe the answer is:
underhand
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">clandestine</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">deceptive</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for underhand that I've seen before include "Done dishonestly" , "Surreptitious" , "Sneaky" , "Way of bowling" , "Crafty" .)