Foolish, fatuous (5)
I believe the answer is:
inane
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">foolish</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(inane can mean silly or foolish)</span><br/ ><br/ >'<span class="explanation-format__original">fatuous</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that fatuous can be written as inane)</span><br/ ><br/ ></span>
(Other definitions for inane that I've seen before include "Silly, witless" , "Idiotic" , "Dull-witted" , "Moronic" , "unimaginative" .)