Good shot brings oppressor to premature end (4)
I believe the answer is:
bull
'good shot' is the definition.
(a bullseye in darts)
'oppressor to premature end' is the wordplay.
'oppressor' becomes 'bully'.
'to premature end' means to remove the last letter (the word finishes early).
'bully' with its final letter removed is 'BULL'.
'brings' is the link.
(Other definitions for bull that I've seen before include "Papal proclamation" , "Male animal" , "Male whale" , "See 20 down" , "Male elephant, say" .)