[Ammako]

Use /fstack in chat and then mouse over it to get the exact frame name.

I don't have game time right now so I can't easily write something and test it on my own right now, since starter accounts can't form groups. Unless someone were willing to help with that.

You'd probably want to do something like this:

local frame = CreateFrame("frame")
frame:RegisterEvent("ADDON_LOADED")
frame:SetScript("OnEvent", function(self, event, ...)
    if select(1, ...) == "Blizzard_CompactRaidFrames" then
        frameName:SetAlpha(0)
        frameName:HookScript("OnEnter", function() frameName:SetAlpha(1) end)
        frameName:HookScript("OnLeave", function() frameName:SetAlpha(0) end)
    end
end)

(In this case frameName doesn't exist; I can't check the right frame name right now and I don't want to make any guesses, so you'll have to get the name of the frame with /fstack and replace frameName with it in the code.)

Also this is untested but this should be the general idea of what you might want to do. If it doesn't work it may just need a few tweaks.