Relish is French with zero added (4)
I believe the answer is:
zest
'relish' is the definition.
(I know that relish can be written as zest)
'is french with zero added' is the wordplay.
I cannot quite understand how this works, but
'zero' could be 'z' and 'z' is present in the answer.
'is french' could be 'est' ('is' in French) and 'est' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
(Other definitions for zest that I've seen before include "Go" , "Drive" , "Enthusiasm - grated lemon peel" , "Zeal" , "Keen excitement - citrus peel" .)