The most common and most likely answer to this crossword clue is the 4 letter word OGEE
I've seen this crossword clue in Independent
O
G
E
E
More clues leading to the result OGEE
- Moulding I reversed, ending on mantelpiece
- Fancy moulding of Trump’s suit
- Old horse half visible in architectural feature
- S-shaped curve over letter
- Regularly scrubbing toughened moulding
- Regular sections of toughened moulding
- Kind of arch, I’ll be put up over either side of entrance
- Curve old girl makes with ease, I hear
Buddy explains!

The straight part
We know that "S-shaped curve" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case s-shaped curve = ogee.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does OGEE mean?
OGEE noun- A double curve in the shape of an elongated S; an object of that shape
- A pointed arch made from two ogees
- An inflection point.
- (aesthetic facial surgery) The malar or cheekbone prominence transitioning into the mid-cheek hollow.
- (distillation) The bubble-shaped chamber of a pot still that connects the swan neck to the pot and allows distillate to expand, condense, and fall back into the pot.