Alark

6 clues
On(for fun)
Happy as --
On ___ (for fun)
For fun, with "on
On ___ (just for fun)
Fresh as ___ . . . ": Wordsworth
Similar answers:
Aaaball
Aaal
Aal
Aalarge
Aalborg
Aalen
Aalii
Aaline
Aaliyah
Aalon
Aals
Aalst
Aalto
Aaltosaxes
Aalu
Aardvark
Aardvarks
Aareaditalaeaer
Aaronhall
Abalance