Intermediated acces = Brokers

In crypto exchanges, these brokers dont exist

clearing is making sure if seller has required money in his account - and both seller and buyer exists (authentication). Clearing house does the netting part.

Netting

minimizes the number of transactions because party owes each other some amount

settlement is writing on the ledger

Final legal rights of moving from one party to another

Clearing House

With blockchain, clearing and settlement happens right away. The accounts need to be pre-fund though. With traditional clearing houses there is a concept of Delayed Settlement - the thing is that, i can buy something without having money OR sell something without having the selling object - the clearing and settlement happens after 1 or 2 days so, me as a seller or buyer have 2 days of time to come up with the selling object or the required money.