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All answers having "Cracks" as clue:

4 Character Answers:

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GAPS

MOTS



5 Character Answers:

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FLAWS

JESTS

QUIPS

RIFTS

SLITS

STABS

TRIES



6 Character Answers:

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CLEFTS



8 Character Answers:

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ATTEMPTS

CREVICES

FISSURES



10 Character Answers:

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FIGURESOUT