Could you knock the stuffing out of him? (3)
I believe the answer is:
guy
'him?' is the definition.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for guy that I've seen before include "send up?" , "Make fun of, tent rope" , "Effigy burnt on a bonfire" , "Mr Fawkes" , "Rope; man" .)