Elated (2,5,4)
(Other definitions for on cloud nine that I've seen before include "Euphoric" , "Extremely happy" , "Transported" , "delighted" , "Elated" .)
'elated' is the definition.
(I know that elated can be written as joyful)
This is all the clue.
(Other definitions for joyful that I've seen before include "On top of the world" , "In state of extreme gladness" , "Feeling great happiness" , "Feeling rapture or delight" , "Happy" .)
'elated' is the definition.
(associated in meaning)
This is the entire clue.
(Other definitions for happy that I've seen before include "Carefree" , "Well-pleased" , "Contented" , "One of the Seven Dwarves" , "Joyous" .)