Re 6D Thanks Mystogre! For those still wrestling with it, it's a homophone, and think in terms of Agent 1, Agent 2, Agent 3.
One of several dodgy clues this week, I'm afraid. 8D is a prime example of this setter's Achilles heel -- clever answer, but no concern for elegance in the clue. When the syntax is that tortured, I just can't be bothered and turn to this website's 'quick solve'. Similarly, in 20D, 'made criticisms'? Why not 'criticised', which is a much better fit? And I guess the abbreviation (first letter) will appear in some dictionary or other, but can't say I've ever seen it used anywhere else.