American whiskey (3)
'american whiskey' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bourbon that I've seen before include "Maize whiskey" , "American whisky; biscuit" , "Henry of Navarre, for one" , "American whiskey - French royal house" , "Rye whiskey" .)
(Other definitions for rye that I've seen before include "21 [GRASS]" , "East Sussex resort" , "One of Cinque Ports" , "Grain - whiskey - port" , "American whisky" .)