Foolish, idiotic (6)
I believe the answer is:
stupid
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">foolish</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">idiotic</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for stupid that I've seen before include "Unintelligent, really thick" , "Crass" , "Ass" , "Daft" , "Lacking wit or intelligence" .)