Indication of illness (7)
I believe the answer is:
symptom
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">indication of illness</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 symptom that I've seen before include "Expression" , "Sign; indication" , "Prodrome" , "It indicates disease" , "Sign of illness" .)