Clustering and classification

I have a dataset with an attribute Grade (ranging from 1 to 3) and a an attribute Explanation.

I converted the numerical Grade from to polynomial and set the label to Grade. This is my target.
Then I converted the nominal Explain attribute to text and split the data in 70% training and 30% testing.
Then I remove the outliers in the trainingset, and use the process document operator. I then tokenize, remove stopwords, stemm and use N-Gramm. The I cross validate and use k-NN for classification.

When i apply my model to  the testdataset, the results are alright, but i would like to try to use a clustering algorithm, instead of a classification alghorithm with target. How do i do this and what do i need to change in my flow?