Deleting column data from Cassandra can be achieved through the Thrift API.  The steps required for deleting columns from a column family using the Thrift API are as follows:

1. Open a connection to Cassandra
2. Define the column family to delete from
3. Define the id of the row to delete column data from
4. Define a column path that serves as the lookup mechanism for the column to delete
5. Specify the timestamp value of the column to delete
6. Specify the consistency level for the remove (delete) operation
7. Invoke the remove function of the Cassandra Thrift Client API and pass in the row id, column path, timestamp, and consistency level.

In a nutshell these are the required steps for deleting data from a column family in Cassandra.  Check out this more precise in detail example of how to delete column from Cassandra columnFamily through the Java programming language.