Answer: certain

AnswerCrossword Clue
CERTAIN

Foolproof

CERTAIN

Particular

CERTAIN

Specified

CERTAIN
Sure
CERTAIN
Positive
CERTAINIn the bag, so to speak
CERTAINCocksure.
CERTAINReliable.
CERTAINSagan's "A ... smile."
CERTAINUnfailing.
CERTAINPositive.
CERTAINLike death and taxes
CERTAINDetermined
CERTAINIndubitable
CERTAINIncontrovertible
CERTAINUnquestionable
CERTAINSome nectar I spilled (7)
CERTAINConfirmed
CERTAINQuite sure
CERTAINDefinite