CSD is the silly 'PC' name for the Chief Hostie who is the 'foreman' (foreperson?) in charge of the other 'Flight Attendants' in the cabin.
Airlines keep changing the titles, just like every other organisation these days. Same job, different title. eg Trains used to have a buffet car attendant, now they have a 'Customer Services Manager.' People used to have secretaries, now they have PA's (Personal Assistant). Shops used to have shop assistants, now they have 'Sales Consultants' etc etc