Cryptic crossword No 2,521

Across

1. Substitute player is on to perform spell (6)
2. For now, I'm following Italian club (7)
3. Visitor from afar crashed - do I stare? (8)
4. Republican, facing mixed results, leaves when the wind blows? (8)
5. Rubbish, manure and rot! Is that over the line? (9)
6. Scratched and chafed, not the worst result (5,4)
7. On trend, not up yet (2,4)
8. Sensors picked up changes (5)
9. Heads off to squat in attic - not dry, it's wet (7)
10. Icy cold and rolling (6)
11. Serpent in skimpy thong (6)
12. At the end of your tongue in garlic-rich languange (6)
13. Shelter when wartime sirens heard sounding, also a boy (8)
14. Taking part, play orc in Return of the King (5)
15. Where friend meets a prince is in 17A city (8)
16. Discover sawn-off gun to end shooting (6)

Down

1. Missing half of Nemo on satellite (4)
2. Dodgy motel? Christ, it's a long ride! (7,4)
3. You never learn! In the end, you might finish up there (3)
4. Bet worthwhile if holding pair? (3)
5. Cold land repels cockney tough guy (6)
6. Snake and its partner losing face (5)
7. Flyer following run in the Strand (6)
8. To be uplifted is at the heart of Bible studies (4)
9. Oddball left on hearing Ed's visited regularly (10)
10. Where to hang out after deleting direct message from admirer? (5)
11. Switch off sports channel early, before announcement of an exercise shoe (10)
12. Knowing disadvantage, debts taken on by heartless scally (11)
13. Queen's Taylor, for example, and line run through capital (9)
14. Leave a light on in agency for old north (9)