There are a few ways to arrive at the same result depending on whether or not you wish to preserve the text attributes of the line of text. To do that:
1. Copy the line of text and paste it back to the page.
2. With the text selected, enter Control+Shift+O to convert the text to outlines.
3. In the Object menu, select Path > Offset path to outline it with another vector. The dialog will have a masurement for the offset. If, after you do the offset, you like it then fine. Otherwise enter Control + Z to undo and try it again with a different amount of offset.
4. Select and ungroup (Control + Shift + G). Select only the original text that you outlined and delete it. Select the outline and assign it a red fill then make it a compound path (Control +8).
5. Position the text on top of the outline. Due to the nature of text you will not be able to use the align features to do this and you just have to do it by eye. Give the text a white fill.
If you don't need to preserve the text attributes, then keep the original path in step 4 and it's ready to print and cut at that point.