The only way to remove that metal frame is to grind off at least two of the plastic tabs arrowed in green in picture below, on one side of the frame. That allows you to lift up that side of the frame and slip it out. After cleaning, you can then put it back in and reproduce the tabs you ground off using some clear epoxy.
It's pretty interventionist.
Instead of that, you could use some Q-tips to clean the area you mention, but you probably won't be able to do a real good job if you have a lot of dirt in there.
Meyer