Scene of conflict a long while back (5)
I believe the answer is:
arena
'scene of conflict' is the definition.
(I've seen this in another clue)
'a long while back' is the wordplay.
'a' becomes 'an'.
'long while' becomes 'era'.
'back' shows that the letters should be reversed in order.
'an'+'era'='anera'
'anera' backwards is 'ARENA'.
(Other definitions for arena that I've seen before include "Sit around here being entertained" , "Place for public events" , "Venue for boxing, circus and other action events" , "place involving conflict?" , "Where gladiatorial contests took place" .)