Answer: spook

AnswerCrossword Clue
SPOOKSpy, slangily
SPOOKEctoplasmic being.
SPOOKHalloween apparition.
SPOOKHeadless horseman, for one.
SPOOKHaunt.
SPOOKHaunt: Colloq.
SPOOKGhost-writer: Slang.
SPOOKHobgoblin.
SPOOKSpirit: Slang.
SPOOKHalloween figure
SPOOKOctober figure
SPOOKApparition
SPOOKPhantom.
SPOOKSpirit
SPOOKCloak-and-dagger person
SPOOKScare slightly
SPOOKBogeyman
SPOOKSpy
SPOOKFun house figure
SPOOKUnnerve
SPOOKMake nervous
spookghost
spookto frighten or become frightened
SPOOKCIA agent, slangily
SPOOKFrighten
SPOOKFrighten, as horses
SPOOKScare
SPOOKHaunted-house figure
SPOOKShake up
SPOOKHalloween haunter
SPOOKCovert operative, slangily
SPOOKFreak out
SPOOKFrighten, as a horse
SPOOKHobgoblin
SPOOKGhost
SPOOKWraith
SPOOKFun-house figure
SPOOKGive the willies
SPOOKScare off
SPOOKCause goose bumps