Related Clues:

• Group in which one feels happiest?
• One constituent of fire may be oxygen, for example
• English allow people in — perhaps into a compound
• Fire - or part of one!
• Component - habitat
• Fire (or part of one)
• Iron, for instance - part of an electric kettle
• Basic chemical unit
• Basic substance or feature
• Primary chemical substance
• Fundamental part of whole
• Ingredient — small amount
• Operative part of an electric kettle
• Component — factor
• Is this what the old Greeks put in the kettle?