Smooth surface partly turned over for race (4)
I believe the answer is:
rush
'race' is the definition.
('rush' can be a synonym of 'race')
'smooth surface partly turned over' is the wordplay.
'partly' indicates a hidden word.
'turned over' says the letters should be written backwards.
'hsur' is hidden in the letters of 'smooth surface'.
'hsur' backwards is 'RUSH'.
'for' acts as a link.
(Other definitions for rush that I've seen before include "Burn rubber" , "Drug-induced euphoria" , "Perform hurriedly; marsh plant" , "Sudden flow of liquid" , "High" .)