Artless; gullible (5)
I believe the answer is:
naive
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">artless</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">gullible</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ ></span>
(Other definitions for naive that I've seen before include "Short on experience" , "Innocently trustful" , "childlike" , "Lacking wisdom and judgement" , "Jejune" .)