Cancel article in book (6)
I believe the answer is:
annual
'book' is the definition.
(annual is a kind of book)
'cancel article in' is the wordplay.
'cancel' becomes 'annul' (annulling is a kind of cancelling).
'article' becomes 'a' (indefinite article).
'in' indicates putting letters inside.
'annul' placed around 'a' is 'ANNUAL'.
(Other definitions for annual that I've seen before include "Book; occurring once a year" , "Occurring once every year" , "Once a year, perhaps a book" , "Plant that lives and dies within one year" , "Occuring once a year" .)