Part of brain disease rarely concealed by a stroke (8)
I believe the answer is:
appestat
'part' is the definition.
Both the answer and definition are singular nouns.
Maybe there's an association between them I don't understand?
'brain disease rarely concealed by a stroke' is the wordplay.
'brain disease rarely' becomes 'pest' (I can't explain this - if you can you should believe this answer much more).
'concealed by' indicates putting letters inside.
'stroke' becomes 'pat' (I have seen 'Gentle stroke ' mean 'pat' so perhaps 'stroke' could also mean 'pat').
'a'+'pat'='apat'
'pest' inserted into 'apat' is 'APPESTAT'.
'of' acts as a link.
Can you help me to learn more?
(Another definition for appestat that I've seen is " Maybe this affects desire to eat".)