Optimistic

3 clues
Upbeat
Hopeful
Happy-go-lucky
Similar answers:
Altruistic
Animistic
Antagonistic
Antisocialistic
Aphoristic
Armistice
Armisticeday
Armisticedays
Artistic
Artisticability
Artistical
Artistically
Artisticlicense
Atavistic
Atheistic
Atomistic
Autistic
Ballistic
Ballisticmussel
Ballistics