There is a fixed distance between the Y-Axis and the left edge of a chart frame which may cause chart labels to be clipped on their left side. Since ClarisWorks displays all chart labels in the same Font, Size, and Style as they appear in your Spreadsheet, change the attributes of those cells so their contents may fit in the allotted space. If this is not desirable then you should find a way to reduce the size of the data itself.
You may choose to customize an ungrouped duplicate of your chart in the graphics environment in order to get wider labels. However, don't duplicate the chart until you've modified your spreadsheet so that all of the labels fit within the frame. Otherwise you'll find that ungrouping the duplicate of your chart will cause those labels that do not fit to disappear. Once ungrouped you can use the graphics tools to create a customized chart but only the original chart will reflect any changes that are made to the spreadsheet in the future.