I use it around my young oaks 4ft to 15ft ones. Clethodim is often directly sprayed around trees, especially Christmas tree farms. Vineyards use it alot too.
Sprayng around the trees without being overly careful you'll be fine. Direct spraying the whole tree, you could burn the leaves some. Like using a boom sprayer in an area.
clethodim needs crop oil to make it work. It's kind of a greasy non-soluable chemical. Needs something to mix with the water.
IT kills grass without killing the weeds. It tames messes around trees, but doesn't completely eliminate them. Some weeds you may have problems with. Definitely worth trying though.