Mark the article I'm after (3)
I believe the answer is:
aim
'mark' is the definition.
(thesaurus)
'the article i'm after' is the wordplay.
'the article' becomes 'a' (indefinite article).
'after' means one lot of letters go next to another.
'a'+'im'='AIM'
(Other definitions for aim that I've seen before include "Purpose, intention" , "Set sights on, target or goal" , "Draw a bead on" , "End" , "Object; intend" .)