What is the exact model name/# of PSU?
Where was this resistor located on the PCB? Existing online pics or providing us some might help.
What is that piece of metal sticking out at the bottom left of your pic? I mean it looks like a wire wound resistor and that is part of the wire, except the wire wraps the other direction and should have went under the end cap on the opposite side based on the visible angle the wire is taking.
I'd first research the first two things I asked above, but ultimately since it is a wire wound type and it looks like the break in the wire is at the bottom as pictured, I would take an x-acto knife and scrap away the coating to expose the wire as low as I can get conductivity from it and then measure resistance between that point and the broken-off-lead nub on the top (as pictured), then based on what (guesstimated) % of the wire was below the break, calculate out the total resistance value based on what you measure, for example if the wire was broken 1/3rd of the way up the resistor and measured 100 ohms to the further end cap lead nub, would be roughly 100 / (2/3) = 150 ohms. This is only an example using fictional numbers.
Considering this is at least a 2W resistor (so was expected to potentially dissipate some heat, a power path rather than signal path placement) the resistance value should be fairly low if it's a load resistor on one of the output rails, maybe sub-200 ohms or less producing some fraction of an amp load for the voltage of the rail it's on, OR fairly high few hundred Kohm or more if a bleeder resistor across the high voltage capacitor on the high side, or IDK if in some other placement more unique to the particular circuit design.