Like a jumping cow, highly delighted (4,3,4)
I believe the answer is:
over the moon
'delighted' is the definition.
('over the moon' means very happy)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for over the moon that I've seen before include "Jumping for joy?" , "Severely restricted" , "a long way into space?" , "euphoric" , "Greatly elated" .)