5d. Does he always live up to his name in a fix (9) ?e?a?????
18a. Military inquiry Administration's brief: WANTED: dead or alive (7,2,6)
4/23d. It's a mighty piece of work for a Latin Scholar (4,6) ?p?s m?????
27a. What it took The Duke to finally get a gong (4,4) ??u? ????
27a. A.P McCoy named for award ??n?
the letters I have for 18a are ~ ?i???n? i? a?t?o? -.
That first i is coming from 1d mastermInd
the first n is coming from 17d oN the ball
the next i is coming from 14d arIes
the a is coming from 5d repairmAn
the t is coming from 6d chitchaT
and the o is coming from 16d loOk-alikes
Magnus Magnusson was the host of Mastermind. While you can say Magnum Opus, you probably would not say Opus Magnum => I think 23d should be Magnus. Not all of the answers in the Guide make sense - Rosebud once had Ewing Ranch mispelt as an answer.