Clingan's draft stock will be almost entirely predicated on his defense/mobility and shooting form. The NBA doesn't care at all about his post moves. They barely care about his rebounding. His ability to pass is seen as a bonus.
His poor FT shooting is going to give them skepticism about him developing a 3-point shot. In order to counteract that, he'll need to figure out the FT line or going to have to actually show he can make 3s (or at least that his form looks promising.) So far, his 2 attempts and summer shootaround videos are not particularly promising. His shot is heavy with poor touch. Had he left this past summer, he could've skated by on mystique (he shoots them in practice and shootarounds!), but he needs form/results now as all prospects are more scrutinized the more film is on them.
His ability to guard in space is the biggest thing. He was high on draft boards due to his rim protection and the possibility of not being a total liability on switches and moving around the court. That liability is what kept Zach Edey in school last season. Clingan is very good in drop coverage when a guard attacks into him, but he's been worse than last year guarding on the perimeter. The muscle and weight he put on to work more in the post has hurt him in this area, along with the injury rust. He's going to have to show a lot more as he gets in game shape to keep his lottery projection.
He'll benefit from some anchoring bias, but he could absolutely slip to the Edey range if it doesn't go the right way.