... a summary of changing prices (6)
I believe the answer is:
precis
'a summary' is the definition.
(I know that precis is a class)
'changing prices' is the wordplay.
'changing' indicates anagramming the letters.
'prices' with letters rearranged gives 'PRECIS'.
'of' is the link.
(Other definitions for precis that I've seen before include "Prices for a summary" , "Summary of the main points" , "Cripes, what a summary!" , "Synopsis, summary" , "Summarize" .)