Vegetable convention, perhaps, held around Southern French city (8)

'french city' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'vegetable convention perhaps held around southern' is the wordplay.
I cannot really see how this works, but
'around' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'southern' could be 's' (abbreviation) and 's' is found in the answer.
'vegetable' could be 'bean' (bean is a kind of vegetable) and 'bean' is present in the leftover letters.
This explanation may well be incorrect...

Can you help me to learn more?