Negative response to a French word (4)
I believe the answer is:
noun
'word' is the definition.
(noun is a kind of word)
'negative response to a french' is the wordplay.
'negative response' becomes 'no' (I've seen this in other clues).
'to a french' becomes 'un' ('a' in French).
'no'+'un'='NOUN'
(Other definitions for noun that I've seen before include "Category of word" , "Naming word (grammar)" , "Word identifying people, things, etc" , "Word referring to person, place or thing" , "Word used as a name for something or person" .)