Punch ingredient? (4)
'punch ingredient?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fist that I've seen before include "handwriting?" , "Punch dispenser" , "Tightly-closed hand" , "Balled hand" , "duke" .)
(Other definitions for knuckle that I've seen before include "A finger-joint" , "Bunch of fives" , "Pork joint from the knee downwards" , "Joint (of veal or pork?)" , "Bone of the fist" .)