Vital (3)
'vital' is the definition.
(I know that vital can be written as important)
This is the entire clue.
(Other definitions for important that I've seen before include "A priority" , "Significant, valuable" , "of great concern" , "Noted" , "Meaningful" .)
'vital' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for essential that I've seen before include "something necessary" , "So is certain oil-production" , "must-have item" , "organic" , "Key" .)
'vital' is the definition.
(key can mean important)
This is all the clue.
(Other definitions for key that I've seen before include "One that locks" , "Vital" , "It can open" , "Lock opener; low island" , "Scale system for music" .)
'vital' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for needed that I've seen before include "'Wanted, required (6)'" , "Essential; called for" , "Required; sounds like worked (dough)" , "Was in want of" , "'Lacked, required (6)'" .)
(Another definition for all-important that I've seen is " Essential, crucial".)