Spoil go (4)
I believe the answer is:
turn
I believe this is a double definition.
'spoil' is the first definition.
(I've seen this in another clue)
'go' is the second definition.
(as in one's go or turn in a game)
(Other definitions for turn that I've seen before include "Refuse" , "Move around an axis, or change" , "Swing round" , "rotation" , "Go; spin (cricket)" .)