Condiment with French wine base put on fish (7)
I believe the answer is:
vinegar
'condiment' is the definition.
(vinegar is a kind of condiment)
'french wine base put on fish' is the wordplay.
'french wine' becomes 'vin' ('wine' in French).
'base' becomes 'e' (Euler's number - base of natural logarithms).
'put on' says to put letters next to each other.
'fish' becomes 'gar' (type of fish).
'vin'+'e'+'gar'='VINEGAR'
'with' is the link.
(Other definitions for vinegar that I've seen before include "Ill-temper" , "Pickling agent" , "Sour-tasting liquid as condiment" , "Pickling fluid" , "Condiment - bad temper" .)