If the wheel is "loose" directly in and out, it's the wheel bearings (excessive clearance).
Best thing to do is jack up that corner on a flat concrete floor and wriggle the wheel.
Grasp at 3 and 9 o'clock and pull/push straight out. If the wheel moves directly in and out, it's the wheel bearings. If it moves in and out, but more at top or bottom, it's the ball joints. Movement will be visible. You may also want to put a finger on the ball joint to check for movement also, it can be fairly small.
Next, pull with right and push with left hand, then reverse. Movement here is a steering linkage problem. Watch the tie rod ends and drag link ball joints -- movement indicates a need to replace. Very unlikely to be the steering box if only one side moves.
Put a prybar under the tire and apply upward force (gently). Distinct movement of more than a couple mm indicates a worn-out lower ball joint. Upper can be bad too, watch for it.
If it's only the one wheel, I'd lay a bet on the wheel bearing. Probably can tighten it up, but if it's been that way any length of time, I'd replace it, they don't like running with excess play.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!