Set aside article out of book (5)
I believe the answer is:
annul
'set aside' is the definition.
(thesaurus)
'article out of book' is the wordplay.
I cannot quite see how this works, but
'article' could be 'an' (indefinite article) and 'an' is located in the answer.
This explanation may well be incorrect...
(Other definitions for annul that I've seen before include "Invalidate" , "Render invalid" , "Obligation" , "Cancel or render void" , "Cancel, say a law" .)