Audio delay within' a Scene

Is there a simple script to delay audio play back, till a certain time within a scene?.

Use yield and WaitForSeconds:

function Start () {
   yield WaitForSeconds(10.0);
   audio.Play();
}

If you control the playing of the clip in code, it's a simple case of setting up a check against Time.time (seconds since game loaded) or Time.timeSinceLevelLoad (self explanatory) and playing the clip once this exceeds a value. You'll need to have a check to see if it isn't playing already, or a bool that tells you you've already played it.

A bare-bones example of a ten-second delay:

if (Time.timeSinceLevelLoad > 10 && !playedIt) {
  audio.Play();
  playedIt = true;
}