CWK - Claris Works file
AppleWorks was the successor to Claris Works
I have no experience opening these files, so the general description under "other files" applies to this and File Juicer may be your best option aside form buying a vintage Mac on eBay
If you need actual conversion rather than "extraction of stuff" from the CWK file, you could take a look at: MacLinkPlus Translators.