Seed a Parisian turned up in vegetable matter (6)
I believe the answer is:
peanut
'seed' is the definition.
(peanut is a kind of seed)
'a parisian turned up in vegetable matter' is the wordplay.
'a parisian' becomes 'un' ('a' in French).
'turned up' says the letters should be written backwards.
'in' indicates putting letters inside.
'vegetable matter' becomes 'peat' (I've seen this in another clue).
'un' back-to-front is 'nu'.
'nu' put into 'peat' is 'PEANUT'.
(Other definitions for peanut that I've seen before include "One of little importance -- ante up (anag)" , "Ante up for the popular snack" , "Ante up for the popular kernel" , "A monkey delicacy" , "sort of butter" .)