Alzheimer's, for instance (8)
I believe the answer is:
dementia
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">alzheimer's for instance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that Alzheimer\\u0027s disease is a type of presenile dementia)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dementia that I've seen before include "Detain me, having distressing condition of old age" , "It's caused by brain diseases" , "Disorder of the mind" , "Detain me in distressed state of old age" , "Severe or persistent mental disorder, often to do with age" .)