Underhand, untrustworthy (9)
I believe the answer is:
deceitful
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">underhand</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">untrustworthy</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for deceitful that I've seen before include "Duplicitous" , "Dishonest" , "unreliable" , "cheating" , "Untruthful" .)