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All answers having "Back up" as clue:

4 Character Answers:

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ABET

AVER

CLOG

COPY

SAVE



5 Character Answers:

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PRONE



6 Character Answers:

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ASSIST

COSIGN

ENSURE

REWIND

SECOND



7 Character Answers:

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CONFIRM

REVERSE

SUPPORT



11 Character Answers:

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CORROBORATE