One of four on a diamond (6)

I believe the answer is:

umpire

(Other definitions for umpire that I've seen before include "Impure (anag) - adjudicator" , "Adjudicator in games such as cricket, tennis etc" , "Arbiter of cricket match" , "Sports arbiter" , "One enforcing the rules in games" .)

I've seen this clue in The New York Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.