Discipline of type of fiction (7)
I believe the answer is:
science
This clue is a double definition.
'discipline' is the first definition.
(science is a kind of discipline)
'type of fiction' is the second definition.
'of' is the link.
(Other definitions for science that I've seen before include "Academic discipline" , "Biology, for example" , "M [MUSEUM]" , "Technology" , "Organised body of knowledge" .)