1. Swain lie on oldest British rocks (8 letters)
6. Crime Colin hatched crossly on K-spar (10)
8. Small island in wishing well (2)
9. see 4 down
10. Back all at reservoir north of Moffat (5)
13. Leave having less agony (2)
15. In so vast an egg (3)
16. Genitive preposition in crofting (2)
18. Evening tin makes fine intrusions (3-7)
21. Island found in ideas terrestrial (6)
22. Winnows or tosses or keeps in order (4)
23. A long time in neon lights (3)

Clues down

1. Notes smile on the calciferous (10)
2. Town in Caithness - a centre for candle-making? (4)
3. Move Cassio (not I) in 1 down near Durness (2)
4, 9 across. I scair a lag off Ayrshire coast (5,5)
5. Golfers assistants set out in East (4)
7. Black Isle oilrigg bay (4)
11. Maria's short avenue (3)
12. Out East relate round in time (5)
14. Groan around a body part (5)
16. Singularly single (3)
17. A light rife around opal (4)
19. A tax on a large vessel (3)
20. Diminutive Italian entombed in granite (2)