Truthful, sincere (6)
I believe the answer is:
honest
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">truthful</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">sincere</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ ></span>
(Other definitions for honest that I've seen before include "Fair and free of deceit" , "Sincere, upright" , "Direct" , "Upright and straightforward" , "Law-abiding" .)