Article on pop art movement (4)
I believe the answer is:
dada
'art movement' is the definition.
(Dada is an example)
'article on pop' is the wordplay.
'article' becomes 'a' (indefinite article).
'on' is a charade indicator (letters next to each other).
'pop' becomes 'dad' ('dad' can be a synonym of 'pop'**).
'a' put after 'dad' is 'DADA'.
(Other definitions for dada that I've seen before include "Precursor of surrealism" , "form of art" , "Irreverent Twentieth Century art movement" , "Art concept" , "Early 20th-century avant-garde art movement" .)