Related Clues:

• A sign of increasing significance
• What's more needed by prodigal son?
• Mathematical solution seen in addition, or vice versa
• Too content for meals-on-wheels
• Too regularly missing allusion
• In addition a number's coming to zero
• In addition (to)
• The opposite of minus
• "But wait, there's more!"
• Grade qualifier
• Word with "ran" or "known as"
• What's more on top of that?
• Besides American players of Star Wars theme
• Positive — addition
• It's available from the Royal Society and from official sources, too