In such cases I set 0-element of the spinner to display the hint. You can also add a question mark after the spinner. After all, this is a common explanation element.
I also abandoned using Spinners due to their limitations, and do one of the following:
Use a Label with its hint, then include the lbl1_FocusChanged (HasFocus As Boolean) event to capture when the label has focus. Then use InputList to give list of options to choice from which then puts the value into the label.
Use an AutoCompleteEditText with its hint, and once again include the FocusChanged event to show the drop down list (acet1.ShowDropDown).
I believe that it is not difficult to create a custom view (CustomSpinner), with a label as button and a listview (I still do not have dedicated myself to custom controls, but who did it, would take a short time) and I think this would be the ideal solution.