Solver BentFranklin writes:
Happy new year and thanks for the many hours of mental exercises!
You are very welcome. This job also provides us with many hours of mental exercises!
Referring to your attachment, I think there are two types of clues that need a little more help for the solver in the form of an indication.
The attachment, as you refer to it, is the document (PDF) in which we explain how to solve our puzzles. We encourage all solvers to read it. It also includes links to Word Salad posts where we give more information on the various clue types. Most of it is a basic introduction to standard American-style cryptic crosswords, but you zero in on the part about some ways that our puzzles may differ from what many US solvers have seen before.
The rebus, where the wordplay is in the answer, is probably unsolvable going forward. No one is going to get BROKEN HEART from EARTH except after solving it from the definition and the cross letters, which makes that clue basically a concise crossword clue with a witty aftertaste. The same goes when the answer is the letter bank, such as your example NURSEMAID. There needs to be some indicator that the sense is reversed. Without it, the implied contract between setter and solver is somewhat strained. I like difficulty, but there still needs to be some route from the clue to the answer. Perhaps something like
BROKEN HEART Earth is the answer to despair (6,5)
About letter banks: One reason this type of clue is not common outside of our puzzles is probably that it is hard to indicate. We certainly agree that “there needs to be some indicator” about which direction the clue goes (from bank to longer word, or vice versa). In fact, we always provide such indicators, including in the example you’re referring to. Or at least we try—it could be that the indicators are not as transparent as we think to people who are not accustomed to the letter bank concept. We’ll do our best to be clearer, at least until those are seen as a standard part of the constructor’s arsenal.
About rebuses: You have a point when you say that it’s difficult to solve a rebus clue through the wordplay alone, and your suggestion to indicate the clue is “backwards” makes sense. However, it is not one we are likely to adopt. When we describe the clue as backwards, it’s to explain it to someone who is new to rebuses, but familiar with cryptics. In reality, E is indeed “Beethoven’s Third”, and O is indeed “second in command”—there is nothing backwards about it.