Answer: four

AnswerCrossword Clue
FOURSquare of the only even prime
FOURQuotation, Part 2
FOURUltimate ball
FOUR...-star review (rave)
FOURBarbershop group
FOURTetrad
FOURFab number, in rock-'n'-roll
FOURNumber of apocalyptic horsemen
FOUR... Corners (Western intersection of note)
FOURThe Fantastic ... (superhero group)
FOURHalfway between ten and ten, if you only count to twelve
FOURLou Gehrig's number
FOURNumber of Roosevelt's freedoms
FOURElevator stop
FOURNumber for golf
FOUR... letter word
FOURCalling birds count, in song
FOURTea time, perhaps
FOURF or H preceder
FOURTrey topper
fourthree plus one
FOURTypical par
FOURStart of an 1863 address
FOURWallace novel, "The ... Just Men"
FOURTea time
FOURBobby Orr's number
FOURPolo team
FOURDeck suit complement
FOURFigure on Orr's back
FOURNearly quitting time?
FOURTeatime
FOUR... striper: naval captain
FOURGrand slam run count
FOURSmall square
FOURHorsemen count
FOURBridge quorum
FOURIV, sometimes
FOUR.. Corners
FOURBrett Favre's number
FOURFinal complement, perhaps