‘… to where the banks were glidden into mud smothered by the sea.’
An English dialect word meaning to ‘glaze over’ or cover with ice.
Source: Henry Williamson, Tarka the Otter: His joyful water-life and death in the two rivers, illus. C.F. Tunnicliffe (Harmondsworth: Puffin Books, 1976 (1927)), p. 35