Today’s Saturday Stumper

Today’s Newsday Saturday Stumper, by Andrew Bell Lewis, is a true Saturday. Not especially tricky, but difficult, for sure. A fine value in puzzling.

Three clues that I especially liked for their novelty: 1-Across, nine letters, “Felonious pier group.” 5-Down, eleven letters, “Timberlake wore them as a teen.” And 13-Down, ten letters, “Start of many a mechanical invention.”

No spoilers: the answers are in the comments.