French blackcurrant liqueur (6)
I believe the answer is:
cassis
'french blackcurrant liqueur' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cassis that I've seen before include "Syrupy blackcurrant liqueur" , "Syrupy blackcurrant drink or flavouring" , "Blackcurrent liqueur" , "Blackcurrant syrup" , "French sweet blackcurrant liqueur" .)