World War I battle (5)
(Other definitions for somme that I've seen before include "bloody fight" , "WW1 battlefield" , "WWI battle site" , "European river" , "World War I battlefield around French river" .)
'world war i battle' is the definition.
(1914 battle in World War One)
This is the entire clue.
(Other definitions for ypres that I've seen before include "WWI battlefield" , "scene of battle" , "WW1 battle site" , "WW1 battle town" , "WW One battle site" .)