reducing disk space consumption

[Ted Yu]

Hi,
I am using DSE 4.8.4
On one node, disk space is low where:

42G /var/lib/cassandra/data/usertable/data-0abea7f0cf9211e5a355bf8dafbfa99c

Using CLI, I dropped keyspace usertable but the data dir above still
consumes 42G.

What action would free this part of disk (I don't need the data) ?

Thanks