Who will use the data that is retrieved from the database after the select? If it will be displayed using the FCK editor, there should be no problem.
Otherwise, you need to use a different encoding (I don't know about FCK editor so I don't know if this is possible).
Or, you need to use a different editor (other than FCK) that will read/write in the proper encoding.
Therefore, decide who will be using the data; that is, what software will they be using to display the data coming from the NCLOB field (for example, Microsoft Word, Notepad, or some other application).
Using that application, create a file that contains Turkish characters.
Write that file into a NCLOB field.
Retrieve the file back and try to display it using the same application.
Make sure the characters are the same and that Oracle has not transformed the Turkish characters.
If all works well, use that application to store data into NCLOB fields.