Finally docked to get a book of charts (5)
I believe the answer is:
atlas
'a book of charts' is the definition.
(I've seen this before)
'finally docked' is the wordplay.
'finally' becomes 'atlast' ('at last' can be a synonym of 'finally').
'docked' means to remove the last letter (to dock can mean to remove the tail of an animal).
'atlast' with its final letter taken off is 'ATLAS'.
'to get' acts as a link.
(Other definitions for atlas that I've seen before include "Holder of world" , "Size of paper once" , "Book of geography" , "collection of charts" , "It appears at the top of the spine" .)