Except on the condition that French article gets fewer (6)
I believe the answer is:
unless
'except on the condition' is the definition.
(I've seen this in another clue)
'french article gets fewer' is the wordplay.
'french article' becomes 'un' (indefinite article in French).
'gets' says to put letters next to each other.
'fewer' becomes 'less' (associated in meaning).
'un'+'less'='UNLESS'
'that' acts as a link.
(Other definitions for unless that I've seen before include "Conjunction meaning except when" , "Otherwise than if" , "Except on the condition that" , "Though" , "Except, save" .)