Related Clues:
- Architect's afterthought
- Name only exists on backward Milan development
- Build a new wing, say
- After-market item
- Home improvement
- Building contractor's job
- Software plug-in
- Optional component
- Bonus feature
- Peripheral device
- Looking back, gesture from father in extension
- Small, as a fee
- Auto option, e.g
- Dad confused by switch for extension
- Theoretical — token