If you want to apply an effect to just part of a video clip, split the video into segments, then apply the effect to one of the segments.
1. | Position the Playhead over a video clip where you want to start the effect (top-left), then from the Edit menu choose “Split Video Clip at Playhead.” Or use the keyboard shortcut Command T. A vertical dividing line appears on the clip under the Playhead. Position the Playhead at the point where you want to split a clip. The split clip. |
2. | Select the clip segment to which you want to add an effect, then choose an effect from the Effects pane. |