Your 'm' is correct and your '?usit' is correct - just add one to the other! If you read (that answer) up the way (mentioned in the clue'), you'll find something that means 'it is strange', with one letter not entered, as per the preamble.
Thank you so much for explaining. I am learning all the time. I get tis rum now. Can you explain 4d to me? For one in MI6, get Bill's old dear, so to speak. (6)I thought spy and got no further....
Anyone got any hints for the final step? I've got the 4 pairs, have used them to come up with a suitable word (given the question formed by the extra letters) but can't see how to move to the alternative title...
4d works like this by the way:
SPIES less I, which is replaced with a common crossword abbreviation for a bill, leaving you with an archaic spelling of an archaic word for 'deer'.
But of a mess but it's the only way it works I think.