She doesn't use animal products, say, in a vehicle (5)
I believe the answer is:
vegan
'she doesn't use animal products' is the definition.
I can't judge whether this defines the answer.
'say in a vehicle' is the wordplay.
'say' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'in' indicates putting letters inside.
'a vehicle' becomes 'van' (van is a kind of vehicle).
'eg' placed within 'van' is 'VEGAN'.
Can you help me to learn more?
(Other definitions for vegan that I've seen before include "one not using animals" , "Avoider of animal products" , "Avoiding animal products" , "One refusing animal products" , "One not eating animals" .)