Authority and income tumbling (9)
I believe the answer is:
dominance
'authority' is the definition.
('dominance' can be a synonym of 'authority')
'and income tumbling' is the wordplay.
'tumbling' indicates anagramming the letters.
'and'+'income'='andincome'
'andincome' is an anagram of 'DOMINANCE'.
(Other definitions for dominance that I've seen before include "Mastery" , "Commanding position" , "top position" , "Control - ascendency" , "Influence (over others)" .)