"Lou Killen always said one of her greatest regrets was teaching "The Wild Rover" to the Clancy Brothers -- they added the claps which are NOT traditional."

Quite correct - Lou did it without the handclaps but with a little riff on the concertina filling the space.

The song went from LK to the Dubliners, and thence to the Clancy Bros. I thought it was the Dubs who introduced the claps, and speeded up the song, as well as replacing Lou's words with a text from Australia.