That is a click style line and fitting. That plastic piece keeps the clip from possibly coming off. The clip holds the line in place and they can wiggle a little. The fitting is seperate and can be replaced. IIRC that year is either an 18mm or 19mm. I know the threaded style (older than yours) is 16mm line with 18mm fitting.
You may want to pull the line and confirm it's the fitting. These don't leak all that often.