Crazed (5)
I believe the answer is:
manic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crazed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for manic that I've seen before include "Pathologically excited" , "demented" , "Crazily excited" , "Berserk" , "Ludicrously busy" .)