African animal returned to eat kill, cause of downfall (7)
I believe the answer is:
undoing
'of downfall' is the definition.
'undoing' can be an answer for 'downfall' (both can mean a loss of power or position). I'm not sure about the 'of' bit.
'african animal returned to eat kill' is the wordplay.
'african animal' becomes 'gnu' (type of antelope. I am not sure about the 'african' bit.).
'returned' says the letters should be written in reverse.
'to eat' indicates putting letters inside.
'kill' becomes 'do in' (to do in is to kill or assassinate).
'gnu' backwards is 'ung'.
'ung' going around 'doin' is 'UNDOING'.
'cause' is the link.
Can you help me to learn more?
(Other definitions for undoing that I've seen before include "Taking apart" , "Ruin - disaster" , "Cause of ruin" , "(A person's) ruin or downfall" .)