If you want the foil to appear on the lines, then I believe you do not want a clipping mask. You want an...
- Place your foil image into Illustrator.
- Copy your line artwork
- Select the Foil and click the Make Mask button on the Transparency Panel (Window > Transparency)
- Click the mask thumbnail on the Transparency panel
- Paste -- You should see your line work paste. You may need to change the color of the strokes to white.
You can then move the line work around to position it within the foil image.
To move the entire thing around, you need to click the artwork thumbnail on the Transparency panel.
You can read more regarding Opacity Masks by reviewing the Illustrator Help Files (scroll down).
Animation reflects Illustrator CS6, but the procedure is the same in newer application versions.
You can accomplish "foil lines" with a clipping mask. However in order to do so you must expand all strokes and create one, compound shape of your line art. Clipping masks do not work with strokes or multiple shapes.
I outlined an Opacity Mask because it is non-destructive. You don't need to alter any artwork and you can easily edit the line art later if necessary.