Match official (7)
'match official' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for referee that I've seen before include "Judge" , "Match official" , "Official to ensure fair play" , "Game official" , "Official who ensures fair play" .)
(Other definitions for linesman that I've seen before include "Official helping referee - telephone repairer" , "Male official with a flag" , "Court official" , "sports official" , "park official" .)