Grandma gets setback in French city (6)
I believe the answer is:
nantes
'french city' is the definition.
(I've seen this before)
'grandma gets setback' is the wordplay.
'grandma' becomes 'nan' (I've seen this before).
'gets' means one lot of letters go next to another.
'setback' becomes 'tes' (I've seen this in other clues).
'nan'+'tes'='NANTES'
'in' is the link.
(Other definitions for nantes that I've seen before include "Western French port" , "Ann set out for the French town" , "Port city on the Loire estuary" , "port abroad" , "Site of historic drownings" .)