I would be tempted to cut off the seatpost clamp part of the tubing, but keep as much metal as I otherwise could and then use an aftermarket seatpost clamp. Bending the steel back would have to be done slowly and with care to avoid further problems since there already is a crack in the tube. If I bought it (I am not bidding), I would drill a small hole at the end of the crack to stop the crack from progressing. Looks like the shim that comes with Nomads is missing, but that is cheap.
My Sherpa, I bought the frame from someone used. He hates those built in clamps, he hired a frame maker to cut off the original Thorn clamp and installed a clamp made by Salsa. Works fine. He eventually sold the bike frame (to me) saying that he loved the bike but that it was the wrong size for him. That aftermarket clamp is working just fine for me.
