Psychological disorder (8)
I believe the answer is:
neurosis
'psychological disorder' is the definition.
(I know that neurosis is a type of psychological disorder)
This is all the clue.
(Other definitions for neurosis that I've seen before include "Resinous sort of mental disorder" , "Mental disorder of resinous origin" , "Mild mental illness not caused by an organic disease" , "Mild mental condition" , "Obsession" .)