Separate book top class won't need (8)
I believe the answer is:
estrange
'separate' is the definition.
(I've seen this before)
'book top class won't need' is the wordplay.
I cannot quite see how this works, but
'class' could be 'range' (both can mean category) and 'range' is located in the answer.
The remaining letters 'est' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for estrange that I've seen before include "Lose friendship" , "separate" , "Reagents (anag.)" , "Alienate from friendship" , "Alienate -- sergeant (anag)" .)