Came a cropper on rocky hill (4)
I believe the answer is:
fell
'hill' is the definition.
(I know that fell is a type of hill)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for fell that I've seen before include "Knock down - mountain" , "Flatten" , "Cut down; hill" , "Lethal" , "Abated" .)