French refusal to engage English? I don't react (4)
I believe the answer is:
neon
'i don't react' is the definition.
(neon is a non-reactive gas)
'french refusal to engage english?' is the wordplay.
'french refusal' becomes 'non' ('no' in French).
'to engage' indicates putting letters inside (some letters get engaged in others).
'english?' becomes 'e' (abbreviation).
'non' going around 'e' is 'NEON'.
(Other definitions for neon that I've seen before include "One of the six inert gasses" , "Type of lighting" , "Gas - light" , "'Chemical element, often used in lights (4)'" , "Atomic number 10" .)