Greek leader soon brought about plucky Priam's end (9)
I believe the answer is:
agamemnon
'greek leader' is the definition.
(I've seen this before)
'soon brought about plucky priam's end' is the wordplay.
'soon' becomes 'anon' (synonyms).
'brought about' means one lot of letters goes inside another.
'plucky' becomes 'game' (I've seen this before).
'end' indicates one should take the final letters.
The final letter of 'priam' is 'm'.
'game'+'m'='gamem'
'anon' placed around 'gamem' is 'AGAMEMNON'.
(Other definitions for agamemnon that I've seen before include "Fabled king soon" , "Leader of Greeks in Trojan War" , "king of old" , "Gk. leader against Troy" , "Greek commander against Troy" .)