Bouquet is the start of a romantic affair (5)
I believe the answer is:
aroma
'bouquet' is the definition.
(bouquet can mean a wine's aroma)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for aroma that I've seen before include "Perfume" , "Distinctive odour" , "Scent - smell" , "Redolence" , "Scent - fragrance" .)