A timestep is usually represented in tecplot as a zone, so to remove a timestep all you need to do is delete the zone. To do that, go to Data/Delete Zone, select a zone, and click on the Delete button.
If you want to see only part of your animation, you can specify where the animation starts and stops.
If you are animating by Time, you can go to Animate/Time and click on the Animate tab. In this dialog you can set the start and end time of the animation.
Or if you are animating zones, then you can go to Animate/Zones and in this dialog you can set the Start Zone and the End Zone for your animation.
Tech Support Lead