It is taken from a book but is about right (7)
I believe the answer is:
excerpt
'it is taken from a book but is' is the definition.
The definition suggests a singular noun which matches the answer.
'right' is the wordplay.
I cannot quite see how this works, but
'right' could be 'r' (common abbreviation) and 'r' is present in the answer.
The remaining letters 'except' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'about' is the link.
Can you help me to learn more?
(Other definitions for excerpt that I've seen before include "Passage from book, play etc" , "Passage cut" , "Passage taken from a larger work" , "Extract from book or film" , "Passage from literature or music" .)