Just a French mother (4)
I believe the answer is:
mere
This clue is a double definition.
'just' is the first definition.
(I've seen this in other clues)
'a french mother' is the second definition.
(I've seen this before)
(Other definitions for mere that I've seen before include "Pool -- pure and simple" , "Lake (poetic); Maori war club" , "Former lake" , "Simply, nothing more than" , "Lake; Wiltshire town" .)