Chronic anxiety about one's health (12)
I believe the answer is:
hypochondria
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">chronic anxiety about one's health</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 hypochondria that I've seen before include "Imagined ill-health" , "Abnormal health worry" , "Chronic anxiety about one's health" , "Morbid anxiety about one's health" , "Imaginary illness" .)