Billy is little different from Buster (6)
I believe the answer is:
bunter
'buster' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'billy is little different from' is the wordplay.
I cannot really understand how this works, but
'from' could be 'un' (I've seen this in other clues) and 'un' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bunter that I've seen before include "Billy -, fict. schoolboy" , "Unending time" , "Billy ......, iconic English fat boy" , "Billy ..., the Owl of the Remove at Greyfriars" .)