Absolutely essential (7)
(Other definitions for vital that I've seen before include "Essential to life, indispensable" , "Crucial" , "Essential; lively" , "Characteristic of life" , "Critical, necessary" .)
(Other definitions for crucial that I've seen before include "'Decisive, critical (7)'" , "Of vital importance" , "Vitally important" , "Pivotal" , "Of paramount importance" .)