Sound of a French mother, advanced in years (9)
I believe the answer is:
undamaged
'sound' is the definition.
(similar in meaning)
'a french mother advanced in years' is the wordplay.
'a french' becomes 'un' ('a' in French).
'mother' becomes 'dam' (female parent of an animal).
'advanced in years' becomes 'aged' (I've seen this in another clue).
'un'+'dam'+'aged'='UNDAMAGED'
'of' acts as a link.
(Other definitions for undamaged that I've seen before include "Not harmed or injured" , "sound" , "without injuries" .)