Mike, are you talking about a 4GTL?
If so it's toeing in too much. Best to get it done at a good tyre company with tracking gauges that fit on the rims. First you have to ask yourself why that one tyre is wearing unevenly and not the other. Has the chassis leg been repaired where the inner radius mounting bolts on? Are both the suspension mounting bushes in good condition? Has the car been in an accident and is the radius arm bent? Has the radius arm been taken off at some point and put back on without the alignment being checked? Is the shock absorber seized on that side?
If all is in order, you'll need to loosen the 3 bolts holding the outer radius arm mounting on - plenty of penetrating oil will be needed. Make sure the car is jacked up with the wheel off the ground. If you put a tyre lever in the gap on the lower part of the mounting, it should move up and down by a small distance. Note that the wheel will move in and out - this will be for your adjustment. Tighten the bolts before driving it to the tyre company. Loosen the bolts when the car is on the ramp and with the wheel on the ground, move the mounting until the correct adjustment is attained. Tighten the bolts, bounce the rear end a few times and re-check. I can't remember the toe in measurement and I have not got my Haynes manual with me, but it's in there somewhere.
Steve