RYOBI Edger not making clean defined edge

Condition of blade
Check the condition of your blade. If the blade is blunt or damaged, it will need to be replaced. A blunt blade has teeth that have rounded off or are no longer visible.

Depth of blade
Check the depth you have the blade set to. Lowering the height of the blade may result in a more defined edge. 

Locking nut
Check the locking nut is secured. If not secured correctly, the blade may spin incorrectly causing an undefined edge.