Answer:

once

Answer	Crossword Clue
ONCE	Children's-story starter
ONCE	Enough, often
ONCE	Formerly

ONCE	Years ago
ONCE	..-over (quick look)
ONCE	"The Raven" opener
ONCE	".. bitten, ..."
ONCE	"... bitten, twice shy"
ONCE	A single time
ONCE	Fairy tale start
ONCE	In the old days

ONCE	On a single occasion
ONCE	Tale starter
ONCE	Word in many limericks
ONCE	Fairy tale starter
ONCE	Fairy-tale start
ONCE	First word in fairy tales
ONCE	Second word of a limerick
ONCE	Story opening

ONCE	Story start
ONCE	Story starter
ONCE	This is often enough
ONCE	Single shot
ONCE	Louise or Turner
ONCE	It's not enough, per Jackie Susann
ONCE	Long ago
ONCE	"Falling Slowly" musical

ONCE	"I'm only gonna say this ... ..."
ONCE	As soon as
ONCE	How often you can lose your virginity
ONCE	"... upon a time"
ONCE	".. bitten..."
ONCE	In the past
ONCE	First word of "The Raven"
ONCE	A long time ago

ONCE	Ever
ONCE	Fairy tale opener
ONCE	Not a second time
ONCE	Fairy tale's opener
ONCE	Never again?