It looks like a bug, when I try to import a .csv file into database table I can't use CLOB data type during importing. Thus I can't import data from .csv file into database when it contains cell with over 4k letters, because of varchar2 can work only with 4k letters length.
I bypass it by creating table with CLOB data, then import .csv file into this table. In this case Import Wizard don't ask me to specify data types for columns as the table is exists already.
For ppl who works with large set of data SQL Developer just unable to do import. Where can I fill a bug?