Hi Laphria, congratulations!
Afraid it's not clear as day to me, and having stared at the completed grid again and again, would be very grateful for clarification.
Is the agent the 1 11, which we're told to leave light?
Or the 18 letter word we're told to shade?
Or is the agent the M---- which is at the end of one line and start of another?
Or do I need to seek out another word entirely?