I'm fairly sure the song was written by Glasgow actor, singer and playwright Roddy Macmillan in about the 1960s. (The other possibility for author is Jim Maclean.) Roddy is not around to tell us more. It may have been made for a play, some of his songs were.
The Macleod lands were Skye, Lewis and Harris, and the earlier times various chucks of the west mainland. I'll leave it for one of the Highland experts to tell you more.
He did a beautiful job of making the text sound like a translation from the Gaelic. I've heard it said both that the tune is Gaelic and is his own, but I've no expertise in the Gaelic tunedom. As for which war and clearance, I suspect Roddy was deliberately vague, making the song more generic in use.