On a high
I believe the answer is:
elated
'on a high' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for elated that I've seen before include "Exultant" , "Full of high-spirited delight" , "Hyped up" , "Overjoyed, happy and excited" , "Jubilant, very pleased" .)