Untouchable (4)
I believe the answer is:
safe
'untouchable' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for safe that I've seen before include "Metal case for storing valuables" , "Uninjured; excellent; lockable cabinet" , "Metal box for security" , "Iron box in which to keep money or important papers" , "Out of harm's way" .)