Possible Clues:

• Asset for sketching the human body?
• Describes accountant to one with encyclopaedic knowledge of those working in fashion business
• American principal takes class briefly with characters - the type particularly good at mathematics
• American from 24 across has brief outline to characters - you'd expect the bookkeeper to have it too
• What the statistician has, for instance, leading the pack on the side of the Number 10s
• Describes accountant to one intellectually capable of working with The Stones
• Accountant's attribute
• Describes accountant to what Leonardo da Vinci had upstairs