Happy as a clam (6)
I believe the answer is:
elated
'happy as a clam' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for elated that I've seen before include "Joyful, uplifted" , "Overjoyed, extremely pleased" , "Jubilant, very pleased" , "Full of high-spirited delight" , "Very pleased, quite high" .)