it looks like caked in dirt so I would go ahead and let her soak in lukewarm water in a tub and then look at it again and try to get a better picture.
if it is a bumble then soak her foot in lukewarm Epson salted water at least 10 to 20 minutes (I had to soak a chickens foot today and could only hold her for 10 minutes in) And then apply this
View attachment 3958054and place a small gauze pad over it and then use vet wrap to hold it in there ( there are videos showing how to wrap a ducks foot with vet wrap aka sports wrap if you search on YouTube).
Leave that on a day or two and then repeat after a few times of doing this the scab should be easy to remove, you have to wear gloves and get all the yellow cheesy stuff out, Then fill the wound with antibiotic ointment and do the gauze pad and wrap again few more times until it’s healed up. I saw what i thought was a really good instructional on bumble foot surgery by the chicken chick here
https://the-chicken-chick.com/bumblefoot-causes-treatment-warning/