Related Clues:

• Expand on
• Enlarge, as one's lead
• Beef up
• Toss in
•     Build on
• Enhance
• Make larger
• Expand upon
• Build an extension on
• Acquire more items for, as a collection
• Buy another item for, as a collection
• Expand, as a collection
• Pile on
• Expand, as a building
• Include in, as a recipe