Alexia from Lexi Made shares a tutorial at The Sewing Rabbit showing how to make a chiffon back top. Most of the top is made from an opaque knit, but the back is a floaty sheer chiffon. She shows the one she made for her little girl, but this would be equally as cute for an adult. If you made the yoke at the top a little lower, it would even hide a bra strap. Go to The Sewing Rabbit to get her tutorial.
[photo from ? on The Sewing Rabbit]