Richer hay transformed pecking order (9)
I believe the answer is:
hierarchy
'pecking order' is the definition.
(synonyms)
'richer hay transformed' is the wordplay.
'transformed' indicates anagramming the letters.
'richer'+'hay'='richerhay'
'richerhay' is an anagram of 'HIERARCHY'.
(Other definitions for hierarchy that I've seen before include "System with grades of authority ranking one above another" , "System with layers of grades of authority" , "Status ranking system" , "priestly government" , "System of status rankings" .)