Top referee's hiding favour (6)
I believe the answer is:
prefer
'favour' is the definition.
(I know that favour can be written as prefer)
'top referee's hiding' is the wordplay.
'hiding' says the answer is hidden in the clue.
'PREFER' can be found hidden inside 'top referees'.
(Other definitions for prefer that I've seen before include "Favour, like better" , "Tend to choose (one thing over another)" , "Like (something) better than another" , "Choose over others" , "as one may with charges" .)