Unprincipled act ended unfortunately (8)
I believe the answer is:
decadent
'unprincipled' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I don't see?
'act ended unfortunately' is the wordplay.
'unfortunately' is an anagram indicator.
'act'+'ended'='actended'
'actended' with letters rearranged gives 'DECADENT'.
Can you help me to learn more?
(Other definitions for decadent that I've seen before include "Showing moral decline" , "Lacking in moral vigour" , "Reflecting cultural decline" , "Morally corrupt" , "Marked by excessive self-indulgence and moral decay" .)