Not just a French trading event (6)

I believe the answer is:

unfair

I'm a little stuck... Click here to teach me more about this clue!

'not just' is the definition.
('unfair' is the opposite to 'just')

'a french trading event' is the wordplay.
'a french' becomes 'un' ('a' in French).
'trading event' becomes 'fair' (I can't justify this - if you can you should believe this answer much more).
'un'+'fair'='UNFAIR'

Can you help me to learn more?

(Other definitions for unfair that I've seen before include "Dirty" , "deceitful" , "Not cricket?" , "Swizz!" , "Unjust, partial" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.