Bait and switch: Each clue below can be answered by changing one letter in the given, capitalized word, and then anagramming the letters. Mostly straightforward this time (I'm all heart). Plenty to go round, so feel free to grab a couple.

RETARD

-1. American President
-2. Scarcity
-3. Room at the top of a house
-4. Blood vessel
-5. Part of a roof
-6. Prolonged angry outburst
-7. Dull, boring
-8. Fine cord
-9. Food storage area
-10. Take into custody
-11. To draw up, revise, edit
-12. Paid announcement of goods for sale
-13. Marked with stripes
-14. Type of bullet
-15. Recompense or requite
-16. Dealer in cloth
-17. Short trip to achieve a specific purpose
-18. To look upon
19. Someone who buys and sells
-20. Elastic band or strap
-21. Straying, deviating from the norm
-22. To trade by exchange

1.Carter

2. dearth
3. garret

4. artery
6. tirade

9. Larder
10. Arrest

Bernie

22. barter

5. rafter

11. redact

All perfect!

17. errand
18. stared

12. Advert
14. Tracer

Gail - #17 is fine, nice try with #18 but it's the wrong tense

Koala -

18. regard

Indeedy!

15. reward
20. garter

8. thread