A uniform-price call auction means that orders are collected, in secret, over a period of time. For example, say over 1 day. All orders are limit orders. Then, at the end of the day, a single price is calculated and all orders are executed at this same price. The price is the one that maximizes the volume that will get exchanged. For example, if the order book depth looks like in the following graph then the intersection point of the bid curve and the ask curve gives the price of highest volume.
Here is a blog post that investigates uniform-price auctions in details: Motoko DeFi
Such auctions can have a lot of advantages over continuous trading as is explained in the post.
Here is an online simulator for the clearing algorithm: Playground
And here is a mops package that implements the clearing algorithm: auction package
We hope to see an auction DEX soon!