Ann Emmert Abbott
“Clip” is short for clipping, as in you clip out the piece you wrote from a copy of the publication. I usually kept a copy of the whole page(s) and the magazine’s cover and any other pages where my article and/or byline and/or bio were listed.
Nowadays, clips are usually photocopies, .PDF files, or even links to writings online.
Yes, it must be published pieces, but not necessarily ones you received pay for. We all start from scratch, and the easiest way to get those first clips is by doing pro bono work. Just a little, to get started.