Possible Clues:

• Was one taking in graduate returning with condiment from sushi bar?
• 'Japanese plant, often eaten with raw fish (6)'
• Condiment that can make the eyes water
• Super-hot paste
• Sushi-bar condiment
• Plant of the mustard family
• Paste often substituted for by dyed horseradish
• It's almost always actually horseradish
• Spicy condiment
• Mustard plant