Pet Simon ordered, showing favouritism (8)
I believe the answer is:
nepotism
'favouritism' is the definition.
(nepotism is a kind of favouritism)
'pet simon ordered' is the wordplay.
'ordered' is an anagram indicator.
'pet'+'simon'='petsimon'
'petsimon' with letters rearranged gives 'NEPOTISM'.
'showing' is the link.
(Other definitions for nepotism that I've seen before include "Pimentos (anag.)" , "Favouritism shown to relatives by those in power" , "The practice of favouring one's relatives in making official appointments" , "Pro-family bias" , "Taking on family" .)