Suggested by 41, the other unclued lights were worms entered backwards in the grid. To comply with the preamble, 6 down needs to be CESTODE (the individual worm) rather than CESTODA (the subclass).

First prize Leslie Verth, Newton Mearns, Glasgow

Runners-up Roslyn Shapland, Ilkeston, Derbyshire. Oenone Green, Feltham, Middlesex