3-letter word for place (verb) + 3-letter word for rocks (diamonds) in 3-letter abbreviation for second, all reversed.
I have finally filled the grid after ten hours' slog. I can sort of see what the larger-than-life characters are and where they go, but have no idea what the instruction about the characters' unchecked down cells means. Enough for today - so much work for such a trivial theme!