A book curtailed at last (5)
I believe the answer is:
atlas
'a book' is the definition.
(atlas is a kind of book)
'curtailed at last' is the wordplay.
'curtailed' means to remove the last letter.
'at'+'last'='atlast'
'atlast' with its final letter taken off is 'ATLAS'.
(Other definitions for atlas that I've seen before include "Set of charts" , "Book of geography" , "Sort of book" , "Plans" , "book of world records?" .)