1916 battle site (5)
I believe the answer is:
somme
'1916 battle site' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for somme that I've seen before include "bloody fight" , "WW1 battle site" , "French river at Amiens" , "World War One battle region" , "French river, scene of 1916 battles" .)