One last change in a book (5)
I believe the answer is:
atlas
'a book' is the definition.
(atlas is a kind of book)
'one last change in' is the wordplay.
'one' becomes 'a'.
'change' indicates anagramming the letters.
'in' is an insertion indicator.
'last' anagrammed gives 'atls'.
'a' going inside 'atls' is 'ATLAS'.
(Other definitions for atlas that I've seen before include "Size of paper once" , "Sky-toting Titan" , "I carry a huge weight" , "Sort of book" , "Mythological Titan (involved with the world of maps?)" .)