Prices tumbling? Goodness me! (6)
I believe the answer is:
cripes
'goodness me' is the definition.
'prices tumbling?' is the wordplay.
'tumbling?' indicates an anagram.
'prices' with letters rearranged gives 'CRIPES'.
(Other definitions for cripes that I've seen before include "Lord" , "Precis (anag) - exclamation" , "Old slang expression of surprise" .)