If the crack is a small one on the front I can tell you how to hide & make it almost invisible !! Since you are likely going to sand it anyway before restaining it,, take some Elmers wood glue and apply a fine line of it along the crack !! Then with your finger rub it into the crack !! Let it sit about 2 or 3 minutes then lightly sand the entire thing along the crack and all. If there is sawdust on other areas brush it toward the crack, using hand & brush ect to press & work it in !! The glue will bond the sawdust into the crack and since it is the same as the wood it should blend in when stained !! You can do two applications if needed letting dry well between coats !!