Are you
Honesty/Truth?
I can be used in many different circumstances,
You can be honest in many situations
Often to set things above the rest.
Honesty is valued in relationships and friendships
However when some people put me in context,
My use is ambiguous at best!
Even though a person may tell the truth, they may not tell the whole truth
But although I'm often well,
Truth is usually favoured
There's one thing I must tell.
Sometimes you "don't want me", you may defend,
Honest answers are sometimes unwelcome, e.g "Does this dress make me look fat?"
But in music you might find me at the end!
Not too sure about this one... Billy Joel has a song called Honesty?