If the clutch is getting old. perhaps you can swap it out with a different one that requires less load, eg. Spin. Halyard for Main Halyard. (although for a J22 I doubt you have that many clutches on deck.)
If it is a
old halyard you can take a section of 7/16" cover (long enough to for the range of halyard settings) and slide it over the existing 5/16" halyard. Then "lock stitch" the new cover section so it doesn't slip and taper the ends down so they will go in and out of the clutch.
It it is a
"new halyard" undersized and you know how to splice you are in luck. Basically all you need to do is a "
bulking splice" where you add a section of core inside the existing core. This works well in small diameter halyards in older sheet stoppers.