Although this could be done by manually creating a new sequence, cutting and pasting the filtered audio clip into it, and then editing this new sequence to replace the original clip, there is a shortcut. Using the Sequence> Nest Items" menu item essentially does these things automatically.
Figure 1 shows an example sequence with just such a situation. A filter is applied to the audio clip named "Interview." The in point was changed, after first rendering it for playback, resulting in the loss of the render file and the need for re-rendering, indicated by the red bar above the timeline.
Figure 1: A multiple track edit, with an audio filter applied to the clip named "Interview"
To avoid the necessity of multiple renders in situations like this, follow the steps below:
Step One
Click on the audio clip that requires rendering to select it (the "interview" clip, in this situation), and then choose "Nest Items" from the Sequence menu. See Figure 2.
Figure 2: The Nest Items Menu
Step Two
This results in the Nest Items dialog box appearing. Enter a name, and enable the "Mixdown Audio" check box. This automatically renders the sequence as it replaces the original clip in your timeline. See Figure 3.
Figure 3: The Nest Items dialog box, with Mixdown Audio enabled
Step Three
You should see something similar to figure 4, with the rendered sequence named "Audio Effects 1" taking the place of the original audio clip. Notice that the red rendering bar has now turned grey as a result of enabling the "Mixdown Audio" checkbox. The in and out points of this sequence clip may now be edited at will, with no need for further rendering.
Figure 4: The finished edit, with the Audio Effect 1 sequence taking the place of the original filtered "interview" clip