I would use a contact, rubber based adhesive if necessary but try squeezing the seal with pliers first, in case the section that grips the metal has sprung open a bit?
John
Thanks John, been to get some glue. It isn't the main door seal on body, its a small strip on the door itself on the leading edge. Not sure what purpose it's for, it runs from top of door to the bottom of the window. And sticks out like a flange that nearly touches the rear edge of the front door.
Anyway.. Its glued on now