Cryptic crossword No 1,865

Across

1. Turned head away to see something unique (3-3)
2. Reindexing scalar components is a source of trouble (6)
3. Fire—one stretching from one end of the east coast to the other (5)
4. Move swiftly around a German in the rear (6)
5. In the show "Homeland," Danes using chlorine gas die at the end (6)
6. The king is in danger, Central European said (5)
7. Cleric and rabbi on vacation, visiting east side of Budapest (6)
8. Quiet person who doesn't have enough cash to "make it rain" (6)
9. Call for spirits when last portions of booze are consumed (3)
10. Needing lotion even more if clerk goes topless (6)
11. Sharp academic identified Icelandic borders (6)
12. Twelve inches to the back (3)
13. Hemingway enters in a different way (6)
14. Excellent East European catching up (6)
15. Echo-y voice:  "It's a jump to the left" (5)
16. Bad mood infecting grandmaster's sponsor (6)
17. A little down, lacking energy and pop (6)
18. Writer of plays seemingly penned by committee, blatantly repulsive (5)
19. One in distress beginning to drink beer? Not true! (6)
20. Teacher is seen in a compromising position (6)
21. The reels overtaking Instagram?  Makes you figure (5)

Down

1. Make beloved American football player put on part of an elf costume? (6)
2. Take off the first part of bulky weight (6)
3. Coffee is brewed, losing zero temperature as a result (6)
4. King announced disasters (6)
5. When I aim at the face, say "Cheese!" (6)
6. Leading House member to give deception about gold reserves from the outset (6)
7. Watch staff in pavilion (6)
8. Playwright using gastrointestinal disorder borders on exploitation (5)
9. Wakes up from acceleration in flight taking off (5)
10. Thai-Kuwaiti dual citizen making poetry, possibly... (5)
11. ...as western nation—one in South America—reduces carbon (5)
12. Nebraska maintains support for the patriarchy? (3)
13. Unending vow to supply grain (3)
14. Sweetheart returns, checking into standard or substandard lodging (7)
15. Wind up drinking orange juice and wine (5)
16. Awards earned by computing right-left symmetries using only the left side (5)
17. Story about mother's tradition in Christmas dinner (6)
18. Extremely sensible feasts being prepared (6)
19. Don's mattress losing volume at the top (3,2)
20. Town official has to turn sharply to the north, then east (5)