1) Down marker 2) Fault caller 3) Grid official 4) Hockey official 5) NFL official 6) Official 7) Official in lawn tennis 8) Official policies on staff 9) One involved in a face-off 10) Sports official 11) Tennis official 12) Wimbledon fault-caller 13) Wimbledon official Found on https://www.crosswordclues.com/clue/linesman