Region's leader among peacemakers moving crowds (6)
I believe the answer is:
droves
'moving crowds' is the definition.
(drove can mean a crowd)
'region's leader among peacemakers' is the wordplay.
'leader' suggests taking the first letters.
'among' indicates putting letters inside.
'peacemakers' becomes 'doves' (dove can mean someone favouring peace).
The initial letter of 'region' is 'r'.
'r' placed within 'doves' is 'DROVES'.
(Other definitions for droves that I've seen before include "Very many, great numbers" , "Moving herds or flocks" , "Moving crowd of people" .)