Hello Pradeep,
As this is a custom table, as said earlier by others, you need to just add that one field at last. After adding the field and saving it in SE11, please remember to adjust it in SE14, or else sometimes it may give some error. And also, if you have table maintenance for it, regenerate it to avoid any problem in SE30 in future.
After transporting to production also, check once for any inconsistency and if needed, adjust in SE14.
Regards,
Anubhab