As to the US nonsense in 14d, in Britain we tend to shorten to the first four letters rather than the outside two. But we will copy the US in future, as we always do!
Castafiore, you need to replace two letters (given by the clue) in a word for comedian with one letter for eccentricity (maths).
If you did what I did you’re probably thinking of the wrong comedian…
So I had an answer for 16a that is an anagram of one of the words. But I'm starting to think it is wrong because I'm totally stuck in the SW in particular. Am I on the right lines?
I still don't get it. I've got a rather obvious five-letter word for comedian, from which I remove two letters as indicated by the clue. But then I have to put the symbol for eccentricity inside that to arrive at my four-letter word. The clue doesn't seem to direct me to do that. So am I going completely wrong here?