What happens soon after Aurora raises matter involving a Parisian (5)
I believe the answer is:
sunup
'what happens soon after aurora' is the definition.
'raises matter involving a parisian' is the wordplay.
'raises' shows that the letters should be reversed in order.
'matter' becomes 'pus' (pus is a kind of matter**).
'involving' means one lot of letters goes inside another.
'a parisian' becomes 'un'.
'pus' written backwards gives 'sup'.
'sup' going around 'un' is 'SUNUP'.
(Other definitions for sunup that I've seen before include "Dawn (American)" , "Literal word for the dawn" , "Solar appearance (US)" , "early in America" , "First light (US), rhymes with travelling over one hundred mph" .)