Possible Clues:

• Angus briefly set up mysterious source of sweetness
• Spurge regularly understood by a few to be grass
• Sweetener source
• Guyana's top cash crop
• What makes a spirit is, Jung regularly observed, mysterious
• Grass suing when not in on secret
• Angus brought back esoteric sweet stuff
• Angus turned up with mysterious source of sweetness
• Major crop of Brazil
• Grand American brought back mysterious crop from tropics