You can lock a column by opening up the context menu for a column (by right clicking the column header or via the overflow menu), and selecting the “Lock column” menu option.
This will prevent users with the “Writer” permission level from editing the values in that particular column. Locked columns will not affect forms, so users will still be able to create form submissions that enter data into a locked column (if you want to prevent this, you can hide the question on the form).
