“A clearing problem” usually means a problem with settling or completing a transaction.

For example:

In banking/finance, “clearing” is the process of verifying and settling payments between banks. A clearing problem could mean a payment is delayed, rejected, or hasn’t been properly matched.

In markets, it can mean buyers and sellers aren’t being matched at the expected price/quantity.

More generally, it can mean something is preventing an obligation or transaction from being finalized.