Match official in Hereford (3)
I believe the answer is:
ref
'match official' is the definition.
(I've seen this in other clues)
'in hereford' is the wordplay.
'in' indicates the answer is hidden within the clue.
'REF' is hidden in the letters of 'hereford'.
(Other definitions for ref that I've seen before include "A diminutive umpire in soccer or boxing" , "Football official (colloq.)" , "Whistleblower (abbr)" , "One traditionally in black" , "Sports umpire" .)