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All answers having "Prohibited" as clue:

4 Character Answers:

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TABU



5 Character Answers:

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FBADE

NIXED

NOTOK

TABOO



6 Character Answers:

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BANNED

BARRED

FORBAD

VETOED



7 Character Answers:

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FORBADE

ILLEGAL

ILLICIT

TABOOED

UNDRESS



8 Character Answers:

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DEBARRED

ENJOINED

OUTLAWED

UNLAWFUL

VERBOTEN



9 Character Answers:

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FORBIDDEN

OFFLIMITS



10 Character Answers:

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CONTRABAND



11 Character Answers:

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OUTOFBOUNDS