He was admitted to the bar in 1871, after which he began practicing law and became connected with a number of important cases tried in Ulster County.

In 1895, he was appointed commissioner to supervise the translation of the Dutch records of Ulster County into English, which he completed in 1898.

He was a New York State Bar Association delegate to the Universal Congress of Lawyers and Jurists, which was held in conjunction with the Louisiana Purchase Exposition in 1904.

[5] In 1909, Governor Charles Evans Hughes appointed him a member of the State Probation Commission to fill a vacancy caused by the resignation of Felix M. Warburg.

[6] Clearwater chaired a New York State Bar Association committee that suggested reforms in the introduction of expert testimony in civil and criminal trials.

He was a New York representative on the American Bar Association committee in opposition to the recall of judges and judicial decisions.

During World War I, he was a member of the International Red Cross, president of the Kingston branch of the National Security League, the Four Minute Men Organization of Ulster County, and the Ten Thousand Dollar Minimum Club of Ulster County, a colonel of the New York State Corps of the War Savings Stamp Army of the United States, and a member of the First, Second, and Third Liberty Loan commissions of Ulster County.

A trustee of Rutgers College, he received an honorary Doctor of Laws degree from there for distinction in public service in 1903.

[10] In 1875, Clearwater married Anna Houghtaling, the daughter of Colonel William D. Farrand of San Francisco, California.