Youngster is taking time to become a Picasso? (6)
I believe the answer is:
cubist
'a picasso?' is the definition.
(Pablo Picasso is an example)
'youngster is taking time' is the wordplay.
'youngster' becomes 'cub' (I've seen this in other clues).
'is taking' says to put letters next to each other.
'time' becomes 'ist' (I can't explain this - if you can you should believe this answer much more).
'cub'+'ist'='CUBIST'
'to become' is the link.
(Other definitions for cubist that I've seen before include "Artist like Picasso" , "Painter like Picasso" , "Early twentieth century style painter" , "Geometrical painter" , "kind of artist" .)