Cryptic crossword No 4,008

Across

1. Came across aphid outbreak, still spreading (10)
2. Tool, type of saw, delivered for migrant worker (4)
3. Hard grafting big shot going without second-in-command (8)
4. With journey incomplete, cancel culture's extremists run amok using unknown mode of transport (8)
5. Cycling enthusiast is missing Grandstand (4)
6. Stage performance? Artists first, old sport (5)
7. Observe riverside town from the East (4)
8. Soldiers make a meal of these vessels (4)
9. Nobles, Oxygen and Fluorine among assortment of gases, conclusively (5)
10. See 4d
11. Relic of avian ancestor (8)
12. Part of dress person itches occasionally (6)
13. Remote controlled by group of units for surveillance expedition (6)
14. Seth loses his crown and gives out whatever is left (8)
15. Creep in rear sections of cattle ranch (4)
16. Some of 19 caught in tangled net of wealth generation (10)
17. Let you have it again or let you off? (6)
18. Sailors in outrage about employer of shipwreck survivor (6)

Down

1. Magnifying glass engineer sees chucked around (9)
2. Less tranquil to raise aloud after a meditation meeting ends (7)
3. After an expression of thanks, Ronyon announced rules, followed by unusual Asian instrument (9)
4. To arrest German man takes majority of Force the day before Pledge of Allegiance (8,7)
5. Character assassinated slain officials (9)
6. Once glorious light taken from flickering holy candle (7)
7. Far from extraordinary to criminalise almost everyone (5)
8. Messed up! So racist! Empire ending in boycott (9)
9. Activate rebel with undercover revolutionary club (9)
10. Put up with tedious conclusion to timeless test (7)
11. Platform surrounded by riled up avant-garde movement (7)
12. Limitless time before era of reproduction (5)
13. Vanilla Ice endlessly pursuing hit with no backing (5)