Can I use my iPhone to clear cache on my computer

In the strictest terms, no, as a local cache would only be local to each individual device. Your iPhone wouldn't have access to your computer's cache and vice versa. You can, however, delete your browsing history from every device signed into your iCloud account by following these instructions - Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch - Apple Support. Cookies and such will remain on your computer, though.

No.