Bishop and former PM briefly in conflict (6)
I believe the answer is:
battle
'conflict' is the definition.
(I know that conflict can be written as battle)
'bishop and former pm briefly' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'and' is a charade indicator (letters next to each other).
'former pm' becomes 'Attlee' (prime minister Clement Attlee).
'briefly' means to remove the last letter.
'attlee' with its last letter taken away is 'attle'.
'b'+'attle'='BATTLE'
'in' acts as a link.
(Other definitions for battle that I've seen before include "Lengthy struggle" , "Sustained conflict" , "Major engagement" , "Midway" , "Military engagement" .)