1: Multiple notes keeping youth leader youthful (4-5)
2: Others acquired skill to turn over a new leaf (7)
3: Point to friendly crowd (5)
4: Gripped by instrument, a longish claw (5)
5: Result of sleeping in currently fashionable paintings (4,5)
6: A requirement to supply food (9)
7: Aboard a ship is shipping magnate (7)
8: Old role for paintings that trick the eye (2,3)
13: Man, having taken a dose of LSD, is overcome by dread in a world of shadows (9)
14: General's horse galloping to dangerous coasts (3,6)
16: It's expedient to engage in habit-forming activity (9)
17: 'Clerks', a hit with stereotypical Generation Xer (7)
19: European country's gold channel (7)
20: Gag about alien in Royal Childrens Hospital (5)
22: Mother is outside with Muslim priests (5)
23: Cite uncertainty about Heisenbergs original principle (5)