Book ends in tacky gimmick (7)
I believe the answer is:
novelty
'gimmick' is the definition.
(thesaurus)
'book ends in tacky' is the wordplay.
'book' becomes 'novel' (novel is a kind of book).
'ends in' says to hollow out the word (remove centre letters) (only the letters at the ends of the words).
'tacky' with its centre taken out is 'ty'.
'novel'+'ty'='NOVELTY'
(Other definitions for novelty that I've seen before include "Small, cheap ornament" , "Original item" , "Something new and strange" , "Small, inexpensive, unusual article" , "Inexpensive toy" .)