Anagrams of Museums, far too difficult for anyone to get those. the other 3 groups are tricky enough

Thanks for the feedback, Big Phil. I will be interested to see how others get on. I thought "a drop" would hopefully the one to give solvers the clue as it looks as if it has to be an anagram and there is not much else you can get out of it.

A challenging grid, I couldn't get anywhere with it, but cool ideas.