shoe-leather

noun
  1. 1

    Leather that is used to make shoes.

  2. 2

    Leather from which shoes are made that is worn out through walking.

adjective
  1. 1

    Basic, old-fashioned or traditional; specifically shoe-leather journalism or shoe-leather reporting: journalism involving walking from place to place observing things and speaking to people, rather than sitting indoors at a desk.

Source: https://en.wiktionary.org/wiki/shoe-leather