Prearrange patient for feature of study? (8)
'feature of study?' is the definition.
(a study might contain a bookcase)
'prearrange patient' is the wordplay.
'prearrange' becomes 'book' (eg booking a table at a restaurant).
'patient' becomes 'case' (synonyms).
'for' is the link.
(Other definitions for bookcase that I've seen before include "Item of furniture", "Reading matter cabinet", "Article of furniture", "It will be shelved", "written works here".)