After-market purchase, 5 letters
Architectural afterthought, 5 letters
Building contractor's job, 5 letters
Building wing, e.g., 5 letters
Computer peripheral, e.g., 5 letters
Cramped handyman's project, 5 letters
Enlarge the house, say, 5 letters
Extra, and this puzzle's title, 5 letters
Final buy-in during a tournament*, 5 letters
Firefox extension, e.g., 5 letters
Give the house a new room: 2 wds., 5 letters
Home builder's afterthought, 5 letters
Increase stadium seating capacity, 5 letters
Last tourney buy-in*, 5 letters
Pepperoni or sprinkles, e.g., 5 letters
Residence afterthought, 5 letters
Supplemental component, 5 letters
Supplementary feature, 5 letters
Webcam, for example, 5 letters
How to make sense of the starred clues, 6 letters
After-market purchases, 6 letters
Enhancing accessories, 6 letters
Optional components, 6 letters
Scanners, PC cameras, etc., 6 letters
Seat warmers, CD player, et al., 6 letters
They're not standard, 6 letters