ACROSS
1. Followed secretly
6. Weed with yellow flowers
12. Headlong rush
17. Danced to jazz
18. Unclear
19. Roaring decade
20. At length (2,7)
21. Famous WW I spy (4,4)
22. Abrade
24. In … and bounds
26. Paved terrace
29. Kidnap payouts
33. Clumsy
36. German wine