Leading defenders all receive the sack for throwing game (5)
I believe the answer is:
darts
'game' is the definition.
(darts is a kind of game)
'leading defenders all receive the sack' is the wordplay.
'leading' indicates taking the first letters (the leading letter of the word).
The initial letters of 'defenders all receive the sack' is 'DARTS'.
'for throwing' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for darts that I've seen before include "Game; moves quickly" , "Tears" , "Game in which missiles are thrown at target" , "They are thrown at targets in pubs" , "Game with board and missiles" .)