Answer: UMP

AnswerCrossword Clue
UMPOne who wears a mask every fourth game
UMPDiamond expert?
UMPPlate cleaner, at times
UMPBase decision maker
UMPCall a strike, say
UMPDuster at home, sometimes
UMPMasked one at home
UMPOfficial in black
UMPOne wearing black at home
UMPDiamond caller
UMPOne stationed at a base
UMPOne who decides what's fair
UMP"Steee-rike!" caller
UMPBaseball official
UMPCall the game
UMPOne crying foul
UMPDiamond judge?
UMPOne who calls strikes and balls
UMPStrike zone enforcer
UMPLittle League official
umpto umpire (to rule on the plays in a game)
UMPDiamond official
UMPFair-or-foul decider
UMPRef
UMPBaseline enforcer
UMPOne who spends the whole game making calls and who might be accused of not watching at all
UMPOne might call you out
UMPRef's counterpart
UMPDiamond arbiter
UMPStrike caller (abbr.)
UMPBallpark figure
UMPBaseball's ref.
UMPMasked official
UMPDiamond authority
UMPStrike caller
UMPOne making decisions at home?
UMPCaller at home
UMPCrouching judge
UMPPlate manager
UMPBaseball arbiter