The most common and most likely answer to this crossword clue is the 4 letter word ARCS
I've seen this crossword clue in The Daily Telegraph
A
R
C
S
More clues leading to the result ARCS
- Quietly leaving fight after retreat in formations not straight
- A Catholic before end of Mass bows
- Battle almost over – discharges required
- They go round in circles
- Bowmen must ignore her curves
- They go round in circles distributing cards, losing a number
- Swerves when winning race, every now and then
- Cars crash on curves
- Cars crashed in curves
- Curves shown by Caprice so regularly
Buddy explains!

The straight part
We know that "curves" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case curves = arcs.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 ARCS mean?
ARCS noun- That part of a circle which a heavenly body appears to pass through as it moves above and below the horizon.
- A continuous part of the circumference of a circle (circular arc) or of another curve.
- A curve, in general.
- A band contained within parallel curves, or something of that shape.
- (electrics) A flow of current across an insulating medium; especially a hot, luminous discharge between either two electrodes or as lightning.
- A story arc.
- A continuous mapping from a real interval (typically [0, 1]) into a space.
- A directed edge.
- The three-point line.
- An arclight.
- To move following a curved path.
- To shape into an arc; to hold in the form of an arc.
- To form an electrical arc.