Department of France, in Picardy region, whose capital is Amiens (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
somme
(Other definitions for somme that I've seen before include "World War one battle where great losses were incurred" , "French river; WW1 battle" , "French river at Amiens" , "Major Great War battle" , "French river known from World War 1" .)