Simple good old fashioned cryptic clues combined with instructions like:

Half of the clues are in the right place. The other half are displaced by the amount hinted at in 16A and 5D. Of those that are in the right place half are to be entered directly and the other half are anagrams.
Oh, yeah--I love those! Take a while, but tons of fun.

Then I finished a Harper's puzzle and the addiction was broken.
Mine was broken when I found this place!