[The Squatter of Amon Rûdh]

It looks as though this could be Head of the White Council, but it relies on some contorted reasoning.

Washed-out black is grey, which implies either Gandalf or Thingol Grey-cloak. If we assume this means Gandalf, metal-head would be Saruman, whom Treebeard describes as having a mind of metal and wheels. The only position nearly occupied by Gandalf but eventually taken by Saruman is head of the White Council. One could say 'White wizard', although Gandalf does eventually become this. The problem seems to be that this isn't a person either, and 'this washed-out black dude' seems to suggest that the answer is Gandalf, or somebody else associated with grey. None of this really addresses 'former agent', which in a conventional cryptic clue would be 'ex spy' or 'ex rep'. All of which is but to say 'search me'.