Complex sentence: In 1968, Elam had a cameo in Sergio Leone's celebrated spaghetti western "Once Upon a Time in the West", where he played one of a trio of gunslingers sent to kill Charles Bronson's character.
Split into simpler sentences: In 1968, Elam had a cameo in Sergio Leone's celebrated spaghetti western "Once Upon a Time in the West". In that film he played one of a trio of gunslingers who were sent to kill Charles Bronson's character.