Non compos mentis (8)
I believe the answer is:
deranged
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">non compos mentis</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for deranged that I've seen before include "irrational" , "Mentally unbalanced" , "Gardened, being quite mad" , "What Ophelia was eventually" , "Crazy" .)