The hospital at Eastleigh was at different times called a "Clearing Hospital", a "Military Hospital" and then a "Casualty Clearing Station". It was not the usual type of CCS; these were usually fairly close to the front line. The Eastleigh hospital was established in May 1915 and acted as a sort of transit camp. Fairly lightly wounded other ranks would arrive at Southampton docks and go a few miles north to Eastleigh where they waited a day or two for suitable train for onward travel to a hospital near home. For part of the time it did take some lightly wounded soldiers and treat them until they could be returned to active service. There were around 1250 beds.
We can be certain that it was, in fact, called a casualty clearing station as we have original correspondence from the commanding officer (Lt Col George Twiss RAMC) in which he refers to his establishment being a CCS. From the Eastleigh & District Local History Society.