Cryptic crossword No 4,060

Across

1. Cigarette student was offered first (5)
2. Almost cement perfect score (6)
3. Greeting extra performing for additional payment (8)
4. Emigration from Germany drops following support at home (5,5)
5. Last of traitors faithful uncovered (4)
6. Supermarket aisles cleared out by old man (4)
7. Observes island research institute splitting darmstadtium (8)
8. Cull moss flourishing (8)
9. Note gallons emptied from bottle (4)
10. Roll Home Secretary provided (4)
11. Oxidisation cracking tin walls (10)
12. Thought about cider put out (8)
13. Encloses a message, but not all of it (6)
14. Bakery binning starts of gingerbread recipe (4)
15. Declare setter's wife should leave bikini? (5)
16. Age restricts final character in book (4)
17. Film rugby contest with referee's face censored (4)
18. International rights activist inspires (4)

Down

1. Famous person outing British royalty on vacation (6)
2. Heads of monkeys are talking away in tree (5)
3. Problem with rats turning up one after the other? (7)
4. Agony develops after trouble rises in Chinese city (8)
5. Tulips she arranged (9)
6. Possible result of polishing off parts of this puzzle? (8)
7. Swimmer gets 50% off squash (7)
8. One casually playing judge defaced gavel (6)
9. Deck scoundrels patrolling river (5)
10. Order wizard, perhaps, to wipe bottom (5)
11. Essential part of glue stick (5)
12. Electronic 90s console found in shop, a surprisingly worthless discovery (5-4)
13. Cleaner regarding demonstration while going round (9)
14. May an inspector answer people? (9)