Possible Clues:

• World record performance, say
• This is achieved by sounding as if there may be 12 in each of them
• It's quite an achievement to have 12 in each of them, by the sound of it
• Sounds like 12 in achievement
• Sound unit of measurement for achievement
• Scoring a 10 in gymnastics, say
• Say imperial units are a remarkable achievement
• Achievement of fate
• Many a Guinness listing
• What an achievement to sound so lengthy!