Fight in civil war brutal, looking back (5)
I believe the answer is:
brawl
'fight' is the definition.
(I know that brawl is a type of fight)
'in civil war brutal looking back' is the wordplay.
'in' says the answer is hidden in the clue.
'looking back' says the letters should be written backwards.
'lwarb' can be found hidden inside 'civil war brutal'.
'lwarb' reversed gives 'BRAWL'.
(Other definitions for brawl that I've seen before include "Riotous fight" , "Rough, noisy fight" , "squabble" , "Public punch-up" , "Noisy crowd fight" .)