Take down hung pictures to clean them. Do not spray water, wood polish, glass cleaner, or any other cleaning agent onto a frame with a mounted picture to make sure that none of the moisture gets inside the mounting and damages the picture.
The glazing in your frame is made of museum-grade UV-coated acrylic. While the advantages include its light weight and resistance to dangerous breaking, it also is highly susceptable to scratching, so it must be handled with care.
To clean acrylic and plexiglass that has slight blemishes or dirt, start off by clearing away any debris. Then, use a premium micro-fiber cloth with soapy water to clean the entire surface area. After wetting the cloth, be sure to lightly blot the surface, rather than applying pressure as you wipe.