tnjk

The green part in the picture is the return pipe. https://rimmerbros.com/Item--i-WJP108200
The green connector seems a puh-fitting, so easy to disconnect, I am not sure where to push it, but I should be easy.
But you need the part attached to that, also seen on the rimmerbro link.
It seems you can only get a complete set of all lines, and you only need one.
I think when you disconnect the fuel line only the content of the return pipe will spill, but have a container at hand to catch the fuel.
You can repair it with a rubber line, but I would prefer to mount a new one, or one from a donor MG.