Double print or a shadow print

You have probably been using non genuine toner, some kinds of this toner is not the same quality as Brother toner and just chews you drum out before its due to be changed. Change the drum and use genuine toner.

Unfortunately your drum unit is shot. The mechanism that cleans excess toner from the drum surface is worn out or has developed a problem. The materials needed to repair are generally not available. If this is happening then the surface of the drum is probably near the end of its usable life anyway. Save yourself a lot of grief and aggravation. Bite the bullet and buy a new drum unit. Office Depot, Staples, etc. usually offer them at about $105.