Cryptic crossword No 3,243

Across

1. See 21ac
2. Try radical workers' leader captured by raid from the right, as occurred in 1970s 17 (5,3)
3. President is a brave leader, with assistant decapitated at work (6,5)
4. A sad piper played, as many did in 17's 10 (9)
5. Square pyramids, triangular prisms, etc... dry ol' shapes, formed with no sensuous surfaces! (9)
6. Moved at anger in country (9)
7. He replaced 11 12 in 17's 1976 25 down after judge essentially forged most of video and note (5,6)
8. Rank type of punishment (8)
9. Dessert rendered unto palace? (10)
10. Asian got hair cut (4)
11. See 11ac
12. Legislation pursuant to power agreement (4)
13. King to win queen's heart, then notice holding an explosive device when looked at afresh! (10)

Down

1. Soldiers stormed seminar (7)
2. Fixed papers etc as per reports (10)
3. Don't start argument and then stop, as some do after going overboard (5)
4. Fare badly, which is a worry (4)
5. Saint arranged music for hospitals (9)
6. Singer keen to return (4)
7. Rank, rotten green gore (7)
8. News that is right outside, like the air in Cairo (5)
9. Instrument with size constant... a "no!" for "take on vacation?" (10)
10. Lovely doubling of constant in complex algebra (9)
11. Freedom fighter, 54, nabbed by pig (7)
12. One has mostly organic fertiliser, like some living in Latin America (7)
13. Language nerd takes on bit of Romanian (5)
14. Places where tea's prepared? (4)
15. Firm excited for intervention (4)