Mogwai have premiered a new video for their new song “Underground.” The track, which features Iggy Pop, is taken from the band’s new compilation album, “Happy Tears,” which will be released on January 8. Mogwai‘s Stuart Braithwaite previously praised Pop in his book “Spaceships Over Glasgow: Mogwai, Mayhem and Misspent Youth”: “Hearing The Stooges had…