Person who examines prices, not fixed (9)
I believe the answer is:
inspector
'person who examines' is the definition.
(someone inspecting something)
'prices not fixed' is the wordplay.
'fixed' indicates anagramming the letters.
'prices'+'not'='pricesnot'
'pricesnot' is an anagram of 'INSPECTOR'.
(Other definitions for inspector that I've seen before include "Bus, train official" , "I look over" , "Lestrade for instance" , "Morse" , "senior cop" .)