A French barrier, old but intact (9)
I believe the answer is:
undamaged
'intact' is the definition.
(I've seen this in another clue)
'a french barrier old' is the wordplay.
'a french' becomes 'un' ('a' in French).
'barrier' becomes 'dam' (dam is a kind of barrier).
'old' becomes 'aged' (similar in meaning).
'un'+'dam'+'aged'='UNDAMAGED'
'but' acts as a link.
(Other definitions for undamaged that I've seen before include "without injuries" , "Not harmed or injured" , "sound" .)