One to Many by Tiburon

Each clue contains a misprint, always in the definition part. In clue order, the correct letters, yield five thematic items (across clues) and a helpful phrase (down clues). In the completed diagram, the main diagonals provide further hints to the theme, and help in orientation. Solvers may thematically colour 22 perimeter squares and should provide the missing item beneath the grid.

Missing item: _ _ _ _

Across
1. Instrument for removing tusks from head of walrus genuine abroad (5)
6. Has a very entertaining occasion on the tiles (5)
10. Girl losing her head after row about plane (7)
11. Horse touching a snake with a hoof (4)
12. A black smear from forge (7)
13. Machines leaving berms lined with trees, say (7)
14. British beer in the park (4)
15. Ill on barely half an ice cream (5)
19. Powerless to capture spare knight - it could be unbeatable (11)
22. When talking, feed on light feasts (5)
24. Cockney proceeds to dig (4)
25. Personal boast, say nothing to rogue (7)
28. Invention in theory recycling propane (7, two words)
29. Part written passage (4)
30. Heading for old hostelry, towards Rome? (7)
31. Advice for young man is due (6, two words)
32. Callous tsar essentially excels (5)
Down
1. Temporary unemployment for actor in audition for farce (5)
2. Wade in river to the ocean almost (4)
3. With sinking hearts octet had started music finals (7)
4. Having a cart clung to horse unyoked (4)
5. Proteins effective for healing cat bones if fractured with ring (11)
6. Jerky with sauce (5)
7. One considering termites grey is to live in a cave (7)
8. Right-footedly poor goalie kicks ball only beyond halfway mark (7)
9. Mentally fetter with hospital drug, right? (5)
16. Tiro - one is over green (7)
17. Yawns after not quite 3 commercials (7)
18. Was very silky, not initially lumpy (7)
20. On economic policy, perhaps to be expected from a coalition of Reds and Greens? (6)
21. There's very little information on ancient Egyptian coin goddess (5)
23. Common ingredients in making latte - sweet to us after a touch of sugar (5)
26. Short distance for second parson (4)
27. Oddly, insanity is now contracted (4)

To enter the competition solvers should send their solution in list format with a normal, cryptic clue to the 8-letter theme word, which must be deduced, to me at Derek Harrison The competition will close on the 1^st February 2002 and the winner will receive a copy of The Crossword Obsession by Coral Amende.