It sure is a diode as is marked "D2".
Those cilindrical diodes are funny because they roll.
You say that it is next to a fuse.
It could help to know in which side of the fuse it is: after or before the power input.
Also will help to know where the other pin goes.
It could be a protection that burns the fuse when you reverse power the circuit. But, as you know, Murphy law says that a device burns faster than the fuse that protects it.
It could be also a series protection diode to prevent the same fault although it adds a Vd drop. But, in this case, it is not easy to fail as you show.
Is if it this kind of diode, I think that you can work out a substitution from is intended functionality.