Can anyone explain how the answer "ogee" fits the clue 23a. "wow, there's zero first on the curve (4) I get the zero part of the clue, but how is "gee" connected to a curve? Very cryptic indeed!
Ogee is a curved shape in architecture.
I think 'wow' and 'gee' have much the same meaning in American slang.
So, if you substitute 'gee' for 'wow' and put the 'o' in front you have the answer.