Young reporter is initially mentioning art movement (6)
I believe the answer is:
cubism
'art movement' is the definition.
(cubism is a kind of art movement)
'young reporter is initially mentioning' is the wordplay.
'young reporter' becomes 'cub' (I've seen this in other clues).
'initially' suggests taking the first letters.
The first letter of 'mentioning' is 'm'.
'cub'+'is'+'m'='CUBISM'
(Other definitions for cubism that I've seen before include "Art style portraying objects as geometric shapes" , "Art style of Picasso" , "Style of e.g. Braque" , "Picasso's movement" , "Art movement using geometric shapes" .)