When you create the html, put the word in the href attribute:
html = '<a href="%s"><span>%s</span></a>' % (word, word)
(NB: you may need to html-escape the words in case they include the characters <, >, &, or ").
You can then extract the word from the QUrl sent by anchorClicked:
word = url.toString()
Alternatively, you could set the href to a key that can be used to look up the word data in a dict.