Second line — the New Orleans street-parade beat (the "second line" is the crowd dancing behind the brass band) as the Meters played it on "Cissy Strut" and "Look-Ka Py Py" with Zigaboo Modeliste on drums. The bass drum plays a tresillo — 1, the "and" of 2, beat 4 — the same 3-3-2 cell as the Cuban habanera, which arrived in New Orleans by the same boats. The snare answers on 2, the "and" of 3 and beat 4, and adds the "and" of 4 in the second bar: the parade drummers' "big four" accent that announces the next bar.
George Porter's bass plays a one-bar riff with a chromatic Eb–E lift into the fifth and a b7–root–fifth turn; the guitar chanks the ninth chord on the tresillo with up-stroke sixteenths after each; the organ comps on the "and" of 2 and the "and" of 4. One chord throughout.
Listen for the kick and guitar agreeing on the tresillo while the snare argues with them — that disagreement is the strut. Compare james-brown-on-the-one (same era, the One instead of the "big four"). Practice: clap the tresillo, stamp the backbeat, then add the "and of 4" every second bar.