I received a(Wells Fargo)check from First Clearing,LLC;St.Louis,Mo.Under "Purpose"it says"Trust Disbursement".?

You probably had a stock brokerage account with a small balance, where First Clearing was the clearing house. First Clearing held your funds in trust for transactions with that broker. There probably was no activity in your account for years and the account was closed out and the small remaining balance was returned to you.