Crackbrained (7)
I believe the answer is:
idiotic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crackbrained</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that crackbrained can be written as idiotic)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for idiotic that I've seen before include "Inviting ridicule" , "Witless" , "Ridiculous" , "Altogether nonsensical" , "Half witted" .)