Managed, with fire, to plunder (7)
I believe the answer is:
ransack
'to plunder' is the definition.
('ransack' can be a synonym of 'plunder')
'managed with fire' is the wordplay.
'managed' becomes 'ran' (both can mean organised or was in charge of).
'with' means one lot of letters go next to another.
'fire' becomes 'sack' (dismiss someone from their job).
'ran'+'sack'='RANSACK'
(Other definitions for ransack that I've seen before include "Pillage, plunder" , "Examine thoroughly" , "Plunder or turn upside down in search" , "Search thoroughly and roughly" , "Search, leaving no stone unturned" .)