To me it looks like the, "we want to try him at a different position to try and develop more versatility" thing we do every TC with a couple guys. It makes sense to me, Clercius has great athleticism, we have a bunch of guys like Corcoran who can fill the roll of the blocking and playing field, but can't do much else. From the slot, Clercius can also pinch the edge with a block and release after on some plays. Plus he plays even bigger than his listed size, so if we want to make TE a thing long term, he would be a prime candidate to pass catch out of a TE alignment.