Went down hill (4)
I believe the answer is:
fell
This clue is a double definition.
'went down' is the first definition.
(fell over)
'hill' is the second definition.
(I know that fell is a type of hill)
(Other definitions for fell that I've seen before include "Upland tract" , "Knock down - or was knocked down?" , "avalanche?" , "Abated" , "Dropped to the ground" .)