Cryptic crossword No 3,659

Across

1. Backing lithium and copper bond with tip of metal brand as "regulation" additive (9)
2. For each one winning silver, Mossad killed several with this device (5)
3. Insensitive, bizarre "fun" having one fish bite head off another (9)
4. Not hard to lose head and endlessly lump together refugees pursuing this (6)
5. Arguing over Nessie's accommodation of household employee (9)
6. Dummy who turns up around military base (9)
7. Write in stone "despicable at heart" (4)
8. Another ungulate emerging from caribou rebirth (6)
9. Die cast: this means the end? Oddly, with challenge, could be vacated (5,8)
10. Cultural headwear beginning to be removed after bus turned away from city centre (8)
11. A 2 down musician and Yellow Brick Road musician carrying fish (9)
12. Report of explosion around second of 2s, which could clear things up (5)
13. Long rejected fashions which are eyesores (5)
14. Ben D. R. died, tragically immobilised (9)
15. See 9ac
16. International pact essentially reversed, and board was less flexible because of this (4)

Down

1. See 21dn
2. See 6dn
3. Famous royal thus framed by fellow in famous city square (7)
4. Gustav's harem upset about line (6)
5. See 21d
6. Checks around old city, e.g. at troubled end of the line, for 21 23 2s (10)
7. Metals appearing symbolically in 11 for some re 21 2 17 (others got 9) (4)
8. Violent terrors seek coups; taking time out they carried explosives in the 21 2 17 (8,7)
9. Ties girls up, which is most awful (9)
10. Schemes see grim destruction (7)
11. Uncovered vase with ends oddly flipped (10)
12. One leads thousands by speech in defiance of ethical norms (9)
13. Deadly game with mystery spell? (7)
14. Quiet temptation which comes from above, quagmires that trap doctor in grim destructive schemes (6,5,8)
15. Pointed attack upsets clubs (4)
16. Vital liquid 17 'let' out of dreadful openings? (5)