No, it doesn't mean the regiment was disbanded.

'Field unit' means both regiments acted together as a single field command: one set of field and staff officers, one flag, ten companies. Supernumary officers either resigned or were reassigned. The regiment appears in the Official Records and inspection reports &c. as the 6th/9th Tennessee Regiment

By the end of 1864, losses eventually forced the consolidated 6th/9th Tennessee Regiment to be combined with other miniscule Tennessee units.