Answer
Lindsey Buckingham was the replacement for Danny Kirwan in Fleetwood Mac. Kirwan was a founding member of the band, but he left in 1972 due to mental health issues. Buckingham joined the band in 1975 and helped to write and produce some of their most successful albums, including Rumours and Tusk. He remained with the band until 1987, when he left to pursue a solo career.