Characteristic group of symptoms (8)
I believe the answer is:
syndrome
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">characteristic group of symptoms</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 syndrome that I've seen before include "Set of symptoms indicating disease" , "Set of symptoms indicating abnormal conditions" , "Particular group of symptoms that always occur together" , "Set of linked symptoms" , "Group of linked symptoms" .)