It's tempting to think of the problems of a dating market as a matching problem because men and women are almost equal in numbers so we just have to match them all up. A clearing problem occurs in markets, (even markets with ~equal supply and demand) when the reserve price of the transaction is not met. For example, the reason I don't own a Ferrari isn't because there isn't 1 Ferrari out there for sale, it's because I don't have enough cash to clear the transaction. Building a more powerful car sales website won't fix this problem. The reserve price is not met.

The dating market is similarly full of people who would like to clear transactions (economist speak for form a relationship), yet cannot because they do not meet the reserve price of those they want to date.

I hope my Ferrari analogy helps to illustrate the core concept, but you have realize that dating markets are even tougher than car markets, because dating is a barter market. For a transaction to clear, there needs to be a double coincidence of wants -- you can't simply use a medium of exchange like dollars to cut the transaction in half. Imagine if to buy a Ferrari you had to find a seller who also happened to need $350k worth of Linux sysadmin work done.