Parisian who introduces revolutionary savoury tart (6)
I believe the answer is:
quiche
'savoury tart' is the definition.
(I've seen this before)
'parisian who introduces revolutionary' is the wordplay.
'parisian who' becomes 'qui' (I've seen this in other clues).
'introduces' means one lot of letters go next to another.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary**).
'qui'+'che'='QUICHE'
(Other definitions for quiche that I've seen before include "French dish?" , "Cheese and bacon pastry dish" , "food" , "Open tart with egg filling" , "Tart filled with savoury ingredients" .)