Ball carrier loses half of boot during rugby set piece (7)
I believe the answer is:
scrotum
'piece' is the definition.
(scrotum is a kind of piece)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for scrotum that I've seen before include "manbag?" , "Wrinkled retainer" , "man's bag" .)