Hindrance to fairness (4)
I believe the answer is:
bias
'hindrance to fairness' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bias that I've seen before include "Favouritism" , "colour" , "Inclination of prejudice" , "One-sided inclination" , "Prejudice, one-sidedness" .)