Index in the story book (5)
I believe the answer is:
table
'index' is the definition.
(I've seen this before)
'in the story book' is the wordplay.
'in the' means one lot of letters goes inside another.
'story' becomes 'tale' (synonyms).
'book' becomes 'b' (abbreviation for book).
'tale' placed around 'b' is 'TABLE'.
(Other definitions for table that I've seen before include "Array of figures" , "Statistical chart" , "Move; furniture" , "Board off which dinner's eaten" , "Horizontal furniture" .)