Concession soon offended popular leaders (3)
I believe the answer is:
sop
'concession' is the definition.
(sop is a kind of concession)
'soon offended popular leaders' is the wordplay.
'leaders' indicates taking the first letters.
The initial letters of 'soon offended popular' is 'SOP'.
(Other definitions for sop that I've seen before include "Minor concession" , "A concession or bribe, once offered to Cerberus" , "usual way of doing things, initially" , "Appeasing bribe" , "Propitiatory offering" .)