Empty-headed (5)
I believe the answer is:
inane
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">empty-headed</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 inane that I've seen before include "Really stupid" , "Silly, fatuous" , "unimaginative" , "Absurd" , "Stupid and silly" .)