Went down hill in north (4)
I believe the answer is:
fell
I believe this clue is a double definition.
'went down' is the first definition.
(fell over)
'hill in north' is the second definition.
(dialect term for a hill)
(Other definitions for fell that I've seen before include "stretch of moorland" , "Fierce" , "Brutal -- high moorland" , "Knock down - came down" , "High moorland or unforested hill in the UK" .)