'Duffer's not half fouled up with ball!' (4)
I believe the answer is:
chip
'ball' is the definition.
(I have seen 'High ball' mean 'chip' so perhaps 'ball' could also mean 'chip')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for chip that I've seen before include "Golf shot from near the green" , "Counter used to represent money in games" , "Murphy sliced" , "Thin piece, of wood or potato say" , "On the shoulder, it's a sign of resentment" .)