Reverse engineering clues

I think clues that require reverse engineering can be fun and add a bit of variety to a puzzle. My feeling is these are popular clues for solvers, but would be interested: 1. to hear other views; do you like to solve these types of clues? 2. Do you like them indicated or are you happy with a simple question mark? Eg, just the QM? Arm with treasure? (4,2) Or with some kind of explicit indication, like: Arm with clue for treasure? (4,2) Or: Arm with treasure, cryptically? (4,2) 3. With the above example, would this have to be a down clue? 4. Finally, do you only like them with required fodder in plain sight: Arm with loot? In this last example, up *can* be an anagrind, so if your answer to 3, was down only, would you be happy with this one as an across solution? Feel free to expand the discussion! Cheers!