Six grand to put in soon in French city (7)
I believe the answer is:
avignon
'french city' is the definition.
(I've seen this before)
'six grand to put in soon' is the wordplay.
'six' becomes 'VI' (roman numeral).
'grand' becomes 'G' (synonyms).
'to put in' indicates putting letters inside.
'soon' becomes 'anon' (synonyms).
'vi'+'g'='vig'
'vig' placed within 'anon' is 'AVIGNON'.
'in' acts as a link.
(Other definitions for avignon that I've seen before include "Where some French danced" , "French residence of popes in 14th century exile" , "European city" , "French city, famous for its 12th century bridge" , "French city, once seat of Popes" .)