Artist originally rejected slow track (5)
I believe the answer is:
lowry
'artist' is the definition.
(I know that Lowry is a painter)
'originally rejected slow track' is the wordplay.
I cannot quite see how this works, but
'track' could be 'ry' (abbreviation for railway) and 'ry' is present in the answer.
The remaining letters 'low' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lowry that I've seen before include "He painted" , "Painter noted for his matchstick figures" , "Painter of industrial Lancashire" , "Painter of bleak scenes" , "L. S. --, English painter" .)