Capital artist stops race (6)
I believe the answer is:
harare
'capital' is the definition.
(capital of Zimbabwe)
'artist stops race' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'stops' means one lot of letters goes inside another (stopping can mean blocking a gap).
'race' becomes 'hare' (hare can mean to run fast).
'ra' placed into 'hare' is 'HARARE'.
(Other definitions for harare that I've seen before include "City in Zimbabwe" , "capital abroad" , "African capital" , "City once called Salisbury" , "Zimbabwe's capital" .)