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All answers having "Upgrade" as clue:

4 Character Answers:

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HILL

REDO

RISE



5 Character Answers:

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AMEND

REFIT



6 Character Answers:

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ASCENT

RERATE

RETOOL

REVAMP

REWIRE



7 Character Answers:

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ELEVATE

ENHANCE

PROMOTE



8 Character Answers:

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RETROFIT



15 Character Answers:

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HOMEIMPROVEMENT