Server Administration :: How To Shrink Table Size

I have a table: desc STG_XML

Name Null Type
------------------------------ -------- ------------------------
ENTITY_ID NOT NULL VARCHAR2(100 CHAR)
ENTITY_TYPE_ID NOT NULL NUMBER
SOURCE_ID NOT NULL VARCHAR2(512 CHAR)
XML_SCHEMA_ID NOT NULL NUMBER
JOB_ID NOT NULL NUMBER
FINGERPRINT NOT NULL VARCHAR2(100 CHAR)
ENTITY_XML_DATA CLOB()
ARCHIVED NUMBER(1)
CREATION_DATE TIMESTAMP(6)
MODIFICATION_DATE TIMESTAMP(6)
ARCHIVING_DATE TIMESTAMP(6)
CREATED_BY VARCHAR2(50 CHAR)
MODIFIED_BY VARCHAR2(50 CHAR)

The problem is that the data of the table are 40GB while on the DB the table holds 400GB! How can I shrink and reuse that space except from drop/recreate and drop/import?

The table has no initial data, so that I can play with the INITIAL parameter. Data are inserted, updated and deleted all the time. I have run DBMS_ADVISOR which recommended to SHRINK table. I have performed the shrink :

alter table STG_XML shrink space COMPACT;

but I haven't gained any space.