Not just a Parisian trade event (6)
I believe the answer is:
unfair
'not just' is the definition.
('unfair' is the opposite to 'just')
'a parisian trade event' is the wordplay.
'a parisian' becomes 'un' ('a' in French).
'trade event' becomes 'fair' (trade fair).
'un'+'fair'='UNFAIR'
(Other definitions for unfair that I've seen before include "Dirty" , "Not equitable, biased" , "Not equitable-or blonde?" , "Weighted" , "'Unjust, inequitable (6)'" .)