Scrap book missing second article (5)
I believe the answer is:
annul
'scrap' is the definition.
(I've seen this before)
'book missing second article' is the wordplay.
I cannot really understand how this works, but
'article' could be 'an' (indefinite article) and 'an' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for annul that I've seen before include "Render invalid" , "Repeal, rescind" , "Recall" , "Make invalid" , "Invalidate" .)