There are multiple bands named Clench:
1. Clench is a band from Sweden who had their most active years between 93-99. In -93 they won swedish music competition Rock-SM (Swedish Championship in Rock) under the name Thrash Inc. They after that went touring all over scandinavia. In their attempts to wash away the branding of "another Europe" (Europe got famous by winning the same competition a couple of years earlier) they changed name to "Clench" in conjunction with recording their first album named "Goatbreath". Clench then went touring again, gaining raving reviews for their live performances. (taken from http://www.metal-archives.com/band.php?id=123442)

The names of the band members should be:

Nisse Bielfeld - Drums, Vocals
Mathias Hellquist - Guitar
Thomas Piehl - Guitar
Örjan Baudin - Bass
Jens Wide - Drums

2. Clench is a project from the United Kingdom active during the 1980s. They specialized in a strange blend of industrial and minimal synth music and put out a single release, "In the Garden", on the seminal avant-garde label Black Dwarf in 1984. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.