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' is a reversal indicator.
'in' is an insertion indicator.
'vegetable matter' becomes 'peat' (I've seen this in another clue).
'un' back-to-front is 'nu'.
'nu' inserted 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" .)