Required English books' assistance to grasp French article (8)
I believe the answer is:
entailed
'required' is the definition.
(thesaurus)
'english books' assistance to grasp french article' is the wordplay.
'english books'' becomes 'ent' (I can't explain this - if you can you should give a lot more credence to this answer).
'assistance' becomes 'aid' (synonyms).
'to grasp' indicates putting letters inside.
'french article' becomes 'le' (french for 'the' - definite article).
'aid' placed around 'le' is 'ailed'.
'ent'+'ailed'='ENTAILED'
(Other definitions for entailed that I've seen before include "As inheritance, limited" , "Dateline? (anag)" , "settled on designated heirs" , "Made necessary by date-line" , "It's involved" .)