Euphoric in the extreme north? (2,3,2,3,5)
I believe the answer is:
on top of the world
This clue is a double definition.
'euphoric' is the first definition.
(I've seen this in another clue)
'in the extreme north?' is the second definition.
(cryptic definition - the top of a world map)
(Other definitions for on top of the world that I've seen before include "as a polar bear, but not as a penguin?" , "Delighted" , "In seventh heaven" , "Elated" , "Penguins aren't" .)