Answer:

twice

Answer	Crossword Clue
TWICE	Once and again
TWICE	How biscotti is baked
TWICE	"Measure ... ..."

TWICE	Doubly
TWICE	Smart way to think?
TWICE	"Once bitten, ......"
TWICE	"The Postman Always Rings ..."
TWICE	How often the postman rings?
TWICE	More than once
TWICE	Not just once
TWICE	Two times

TWICE	"...bitten, ... shy"
TWICE	Double
TWICE	A couple of times
TWICE	Now and again?
TWICE	Another time
TWICE	A second time
TWICE	Again
TWICE	Doubly.

TWICE	Bis.
TWICE	What "bis" means.
TWICE	"...-Told Tales."
TWICE	In doubled quantity.
TWICE	Once again.
TWICE	" . . . bitten, ... shy"
TWICE	"Once bitten, ... . . . "
TWICE	As much again

TWICE	How Cain's postman rings
TWICE	... told (trite)
TWICE	Bis
TWICE	Hawthorne's "... Told Tales"
TWICE	What "bi-" means
TWICE	How often Santa checks his list
TWICE	x 2
TWICE	The Process of Elimination: In the answer to each starred clue, cross out any letter that appears ...; then read the letters that remain

TWICE	Time and time again?
TWICE	Over again
TWICE	What "bis" means
TWICE	How often, at most, one can be elected U.S. president
TWICE	How the careful think