Known as the “white Zulu”, he was a vocal critic of the apartheid government which ruled until 1994.
The British-born musician, who uniquely blended western and Zulu music, was diagnosed with cancer in 2015.
His best known hit Asimbonanga, released in 1987, was dedicated to Nelson Mandela.
Meaning “We have not seen him” in Zulu, the song was one of the first to openly call for Mandela’s release.
At the time, the future first black president of South Africa was still in jail and considered a threat to the apartheid state.
Clegg – a white man who learnt to speak and sing in Zulu – became a symbol of democratic South Africa and was chosen to sing at Nelson Mandela’s memorial service in 2013.
His long-time music manager, Ronny Quinn, who announced the news of his death, said Clegg left “deep footprints in the hearts of every person that considers himself or herself to be an African”.
“He showed us what it was to assimilate to and embrace other cultures without losing your identity.”
Tributes have been pouring in for Clegg, including from the South African government.
Clegg began his career 40 years ago with Juluka, a mixed-race band, which he formed with the black guitarist, Sipho Mchunu.
At that time, much of his music was banned from the airwaves and his public performances were limited until apartheid ended in 1994.
“We had to find our way around a myriad of laws that prevented us from mixing across racial lines,” he told AFP news agency in 2017.