Clean Deleted Field from Database
using drush:

$ drush eval "field_purge_batch(500)"


you might have to run a few times, or increase the $batch_size
then there might still be field_deleted and field_deleted_revision tables, even after running cron

query

SELECT * FROM `field_config` WHERE `deleted` = 1
SELECT * FROM `field_config_instance` WHERE `deleted` = 1


if you come up empty, you can safely delete those leftover tables