Ye the panel filter sits inside the airbox and filters the air the way Renault intended it to be. If you fit an ITG panel filter instead of a standard one which is made from paper, it isn't standard as it came out of the factory, but is as near as damm it! Lol! The ITG panel filters are direct replacements for the original and just allow greater airflow through them than standard paper ones. So you get a better noise and sometimes a bit more performance (although it is negligable if there is any power gains at all). The good thing about them though, is that unlike standard paper air filters, performance panel filters, such as the ITG don't really require changing. There are other brands too, like K & N. But most Clio owners on here buy ITG because of several reasons.
1. They are British designed and built (in Coventry)
2. ITG test all their filters on the actual car they are designed for, where as most companies just copy originals in design but with different meterials (usually cotton or a guaze type thing)
3. The are reasonably priced (best price on the net is Camskill @ £40 delivered).
4. They are recommended by lots of people.
Hope this helps.