Possible Clues:

• In Germany, this has to have a twisted tail
• In Germany it must have a tail
• Necessary, else stain will show
• In Germany, butchering the ending is mandatory
• 'Absolutely necessary, required (9)'
• Eat in less irregularly — that’s vital!
• Fundamental crack lets in sea
• Heard eau de cologne found in another aisle is a mush-have
• Vital German city -- it rises above a lake
• Very important