Conflict in unruly bar row involving ecstasy (4,3)
I believe the answer is:
boer war
'conflict' is the definition.
(19th-century conflict)
'unruly bar row involving ecstasy' is the wordplay.
'unruly' indicates anagramming the letters.
'involving' means one lot of letters goes inside another.
'ecstasy' becomes 'E' (informal term for the drug).
'bar'+'row'='barrow'
'barrow' with letters rearranged gives 'borwar'.
'borwar' going around 'e' is 'BOER WAR'.
'in' acts as a link.
(Other definitions for boer war that I've seen before include "South African scene of conflict 1899-1902" , "hostilities" , "Either of two conflicts fought by Britain in S Africa" , "'One of two armed conflicts in southern Africa (4,3)'" , "Conflict in southern Africa" .)