Fixed higher by arrangement (5)
I believe the answer is:
setup
'arrangement' is the definition.
(thesaurus)
'fixed higher by' is the wordplay.
'fixed' becomes 'set' (both can mean decided or determined).
'higher' becomes 'up'.
'by' is a charade indicator (letters next to each other).
'set'+'up'='SETUP'
(Other definitions for setup that I've seen before include "Organisation (informal)" , "Fix" .)