How is clustering different from unsupervised learning as both follows same approach, understand patterns in data? I mean why it is kept in the traditional approach, cant we use it as a machine learning approach too?

I agree. Applying clustering technique to big data wouldn't be practicable due to the volume and variety of the data set. Hence, letting a computer accomplish this task for us (unsupervised learning) is the best way to go.

I guess clustering is in traditional methods of data science which is used on traditional and relatively small data where unsupervised learning is used in ML.