Mild mental disorder (8)
I believe the answer is:
neurosis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mild mental disorder</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 neurosis that I've seen before include "Mild mental condition" , "Mild mental problem" , "So insure against the nervous disorder" , "Trouble in mind" , "Mild mental illness often involving anxiety" .)