Person, for instance, in the forefront of vegetarianism (5)
I believe the answer is:
vegan
'person' is the definition.
(vegan is a kind of person)
'for instance in the forefront of vegetarianism' is the wordplay.
I cannot really understand how this works, but
'for instance' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is found within the answer.
'forefront' could be 'van' (van can mean the front part of something) and 'van' is present in the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for vegan that I've seen before include "One not eating or using animal products" , "One not eating animals" , "Person refraining from using animal products in any way" , "Strict vegetarian" , "One avoiding all animal-based food" .)