Frenchman joined a union that's modernised (7)
I believe the answer is:
renewed
'a union that's modernised' is the definition.
I can't tell whether this defines the answer.
'frenchman joined' is the wordplay.
'frenchman' becomes 'rene' (common French name).
'joined' becomes 'we'd' (I've seen this in another clue).
'rene'+'wed'='RENEWED'
Can you help me to learn more?
(Other definitions for renewed that I've seen before include "Reinvigorated" , "With restored vigour" , "Gave fresh life to" , "Began again" .)