After ten years leaders in Northern Territory degenerate (8)
I believe the answer is:
decadent
'degenerate' is the definition.
(I know that degenerate can be written as decadent)
'after ten years leaders in northern territory' is the wordplay.
'after' means one lot of letters go next to another.
'ten years' becomes 'decade' (a decade is ten years).
'leaders in' suggests taking the first letters.
The first letters of 'northern territory' is 'nt'.
'decade' next to 'nt' is 'DECADENT'.
(Other definitions for decadent that I've seen before include "Reprobate" , "Morally deficient; declining" , "Morally corrupt" , "Self-indulgent or immoral" , "Depraved" .)