Race difficulty? (8)
I believe the answer is:
handicap
I believe this clue is a double definition.
'race' is the first definition.
(I've seen this before)
'difficulty?' is the second definition.
(I know that handicap is a type of difficulty)
(Other definitions for handicap that I've seen before include "golfer's measure of skill" , "Disadvantage to offset an advantage in golf" , "Impediment, hindrance" , "Put at a disadvantage" , "Place at a disadvantage" .)