Your syntax is all wrong. Per Dave, you should be using <link> and not an <a> tag.
Also, you have anchor text in your link. This link isn’t the same as a hyperlink that is embedded in the copy of a website. It will not be visible to users but is supposed to instruct search engines on which page is the correct one to index. Also, you need to have the absolute path of the page and not just the URI.
Here is what it should look like,
<link rel=”canonical” href=http://www.example.com />