A flash republican covering up university affair (5)
I believe the answer is:
amour
'affair' is the definition.
(amour can mean a love affair)
'a flash republican covering up university' is the wordplay.
'flash' becomes 'mo' (both can mean a very short period of time).
'republican' becomes 'r' (abbreviation).
'covering up' means one lot of letters goes inside another.
'university' becomes 'u' (abbreviation for university).
'mo'+'r'='mor'
'mor' going around 'u' is 'mour'.
'a'+'mour'='AMOUR'
(Other definitions for amour that I've seen before include "Fling" , "Affair of the heart" , "20 [AFFAIR]" , "Love affair, perhaps secret" , "Result of Cupid's darts" .)