Starts with frankfurter and teewurst as Bunter (3)
I believe the answer is:
'as bunter' is the definition.
(I've seen this before)
'starts with frankfurter and teewurst' is the wordplay.
'starts with' indicates taking the first letters.
The first letters of 'frankfurter and teewurst' is 'FAT'.
(Other definitions for fat that I've seen before include "and 24: Overpaid City type" , "Overweight, stout" , "Cooking grease" , "As Bunter" , "Corpulent; little (chance)" .)