1937 Cent -Brass

I would avoid "cleaning" at all costs. It will destroy the value of any coin. "Restoration" is acceptable to some using very specific careful techniques, but you are likely well advised to leave well enough alone. Posting a picture of the issue would help. Things you might want to restore would be a coin with corrosive PVC residue from a bad holder, for instance.

There are no circulating brass 1937 cents. There is a brass pattern cent, but none have ever been found circulating as far as I know. If your coin was one of these it would be immediately obvious. It has upset dies and is obviously an unusual colour. Maybe 5 to 10 known.

I wouldn't get too focused on the weight. It is 3.1g vs. the normal 3.2g. That difference could easily result from random planchet error and would not mean it is brass. If you find an upset dies 1937 it is quite possibly brass, but regardless is a treasure!