What a whittler whittles

WOOD

Think of the natural material that carvers shape into spoons or figurines—it grows on trees and can be split into kindling.

A whittler is someone who carves shapes by cutting small pieces from a material, most commonly wood. The clue plays on the action itself—"whittles" hints at both the verb (to whittle) and the object being worked on. Since wood is the traditional material for whittling, it’s the straightforward answer here. No tricks or wordplay, just a direct definition.