The French experiment is most recent (6)
I believe the answer is:
latest
'most recent' is the definition.
('late' can be similar in meaning to 'recent')
'the french experiment' is the wordplay.
'the french' becomes 'la'.
'experiment' becomes 'test' (test is a kind of experiment).
'la'+'test'='LATEST'
'is' acts as a link.
(Other definitions for latest that I've seen before include "Most recent or most unpunctual" , "Up-to-the-minute" , "Most recent or most tardy" , "delayed more than all others" , "style of today" .)