Brickwork

Enter the solutions to the clues in their numbered layers of the wall. Each word must be an anagram of its neighbours, plus or minus one letter.

1 Sleep 2 Sound of distant thunder 3 Madagascan primate 4 Donkey-horse crossbreed 5 Tree 6 Unit of distance 7 Substance produced by slugs 8 Figure of speech 9 Thrown or fired object