Clark was the strike partner of John Toshack at Cardiff City and was famously the man who scored a wining goal for Cardiff against Real Madrid in 1971 at Ninian Park.
Clark has been ill for a while but his death has come as a shock.
His former team mate Toshack spoke today.
"I was aware that he hadn't been too well and was struggling," said the Wales manager.
"From a personal point of view, I have to say how much I appreciated the help I got from him when I started playing with him as a youngster in a very experienced side.
"I probably wouldn't have been able to have the start I did in club football if I wasn't playing with someone as generous as Clarky was in his game.
"I'm just very, very sad about what's happened and would like to take the opportunity to pay my respects to his wife and family."
Clark joined City from Huddersfield and also played for Bournemouth, Millwall and Bristol City.
RIP.