Clean it from what?
Still have paint on it? You're not done sanding and scraping.
Saw dust? Use a tack cloth.
Water staining/discoloration? Oxalic acid, aka wood bleach.
You will want to see what it looks like without stain. Use some mineral spirits on a rag. It will darken the wood and give you an idea what it will look like with just a varnish. The Mineral spirits will dry and not effect your final finish.