Artist's line on the ground? (5)
I believe the answer is:
lowry
'artist's' is the definition.
(I've seen this before)
'line on the ground?' is the wordplay.
'line' becomes 'ry' (abbreviation for railway).
'on' is a charade indicator (letters next to each other).
'the ground?' becomes 'low' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ry' after 'low' is 'LOWRY'.
Can you help me to learn more?
(Other definitions for lowry that I've seen before include "English painter noted for his stick people" , "He painted" , "Painter of industrial Lancashire" , "Painter noted for his matchstick figures" , "Painter of bleak scenes" .)