To reduce something with the use of a file. A noun or pronoun can be used between "file" and "down." Do you think I can just file down the corn on my foot?
file something down
to level off a protrusion by filing. File this edge down so no one gets cut on it.Please file down this edge.
file down
v.
To cause wear on something by rubbing against or filing it, reducing its size: I filed down my fingernails before the party. The dentist filed the jagged tooth down.