After short time Pasteur processed cheap cheese (9)
I believe the answer is:
mousetrap
'cheap cheese' is the definition.
(I've seen this before)
'after short time pasteur processed' is the wordplay.
'after' means one lot of letters go next to another.
'short time' becomes 'mo' (slang abbreviation for 'moment').
'processed' is an anagram indicator.
'pasteur' with letters rearranged gives 'usetrap'.
'mo' put next to 'usetrap' is 'MOUSETRAP'.
(Other definitions for mousetrap that I've seen before include "Snare for vermin" , "Boring hard cheese (informal)" , "Cheap cheese" , "Poor cheese (colloq.)" , "Poor-quality cheese" .)