The Collaborative International Dictionary of English v.0.48:

Clamp \Clamp\ (kl[a^]mp), v. t. [imp. & p. p. Clamped
   (kl[a^]mt; 215) p. pr. & vb. n. Clamping.]
   1. To fasten with a clamp or clamps; to apply a clamp to; to
      place in a clamp.
      [1913 Webster]

   2. To cover, as vegetables, with earth. [Eng.]
      [1913 Webster]