Clair is a Pegasus Knight in Alm's route.  The rest is a quote from the Fire Emblem Wiki. [WARNING: CLAIR ONLY HAS ONE LINE, SO THE QUOTES HERE ARE TAKEN FROM THE GAME]

"A headstrong and fearless young noblewoman, Clair has an overbearing nature, which is her one big flaw, not that she pays it any mind. She is also a cheery and sociable individual who loves to interact with any and everyone. She values her impression on others and speaks in an extremely formal and often eccentric manner. In the past, she was somewhat childish and impetuous, and while she has matured since then because of the war, she misses the carefree days of the past."

Clair's english voice is Alexis Tipton. https://youtu.be/4tr3F08iwv0?t=847