Crazy person’s rich teatime fare (9)
I believe the answer is:
fruitcake
I believe this is a double definition.
'crazy person's' is the first definition.
(fruitcake can informally mean a crazy person)
'rich teatime fare' is the second definition.
(rich snack)
(Other definitions for fruitcake that I've seen before include "fancy?" , "Nutty" , "Dundee dessert - madman" , "one off his trolley" , "Eccentric person" .)