Remove article from book (5)
I believe the answer is:
annul
'remove' is the definition.
(thesaurus)
'article from book' is the wordplay.
I cannot really see how this works, but
'article' could be 'an' (indefinite article) and 'an' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for annul that I've seen before include "Cancel officially" , "Scrap" , "Quash" , "Invalidate" , "Render invalid" .)