Simplistic (5)

I believe the answer is:
naive
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">simplistic</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for naive that I've seen before include "Unaffectedly trusting" , "Jejune" , "Innocent and credulous" , "Foolish, inexperienced" , "childlike" .)