Story book is a gift (6)
I believe the answer is:
talent
'is a gift' is the definition.
(I've seen this before)
'story book' is the wordplay.
'story' becomes 'tale' ('tale' can be a synonym of 'story').
'book' becomes 'nt' (I've seen this in other clues).
'tale'+'nt'='TALENT'
(Other definitions for talent that I've seen before include "Gift - aptitude" , "Biblical coin" , "Natural skill or flair" , "ancient coin" , "Special or very great ability" .)