15 possible answers to
Answers with 4 characters: RISE Answers with 5 characters: EXALT KEYUP REVUP AMPUP Answers with 6 characters: DEEPEN HEATUP RAMPUP STEPUP Answers with 7 characters: ENHANCE ESCALTE SHARPEN Answers with 8 characters: ESCALATE HEIGHTEN Answers with 9 characters: AGGRAVATE