Either chain, or sprocket(s) or chainwheel is worn. (Almost) The only cure is replacement. Start with chain, as it's usually the cheapest part. If problem remains, or if new chain is a visibly poor fit on old sprocket(s), replace sprocket(s) too. If problem still remains, replace chainring(s) /crankset. ( some sprockets/chainrings can be flipped over and run in "reverse". Since wear is on one side, this will get you some more use out of them.)
That's the trouble with a word like "skips", it allows for some interpretation. Skips-as-in-trying-to-shift can indeed be poor adjustment, or a flexy/damaged frame under a strong rider. Skip-w/o-shift is another thing entirely.