The 'right fix' depends on _how_loose_ the joint is. 'Shimming' the joint to restore tightness is a time-honored way.
If a single piece of 'grocery store brown paper bag' (assuming you can still _get_ those somewhere :), will tighten up the joint, then that's a reasonable solution, with regular wood glue. If things are open _more_ than that, you'll want something with expanding filler characteristics. micro-balloons ??