Money is most important (9)
I believe the answer is:
principal
This clue is a triple definition!
'money' is the first definition.
(thesaurus)
'is most' is the second definition.
(thesaurus)
'important' is the third definition.
(similar in meaning)
(Other definitions for principal that I've seen before include "Headmaster" , "head of school" , "top man" , "Chief, main" , "Primary" .)