Answer:

one

Answer	Crossword Clue
ONE	It appears twice in the Fibonacci sequence
ONE	Common typo for an exclamation point
ONE	Unnamed person

ONE	Binary digit
ONE	Number on a foam finger
ONE	Last number in a countdown
ONE	It's 50/50
ONE	Number of Q tiles in Scrabble
ONE	What a raised index finger may stand for
ONE	Number of seasons played by baseball's Seattle Pilots
ONE	Half and half?

ONE	2000 Beatles album ... or its peak position on Billboard
ONE	It's next to nothing
ONE	Washington's bill
ONE	Yellow ball in pool
ONE	Whole
ONE	Phone button that lacks letters
ONE	Any nonzero number raised to the power of zero
ONE	Prime factor

ONE	Telephone button that doesn't have letters
ONE	Digit in binary code
ONE	Gender-neutral pronoun
ONE	Its square equals its square root
ONE	United
ONE	A quarter to four?
ONE	Inseparable
ONE	See 6-Down

ONE	Wedded
ONE	See 23-Across
ONE	Bill in a tip jar
ONE	Any nonzero number to the zeroth power
ONE	Hour after midnight
ONE	Unified
ONE	Meaning of a raised index finger
ONE	Liftoff preceder

ONE	Cosine of 0
ONE	Opening number?
ONE	Not you specifically
ONE	Small square
ONE	... Direction (boy band)