Right on the old type of whisky (3)
I believe the answer is:
rye
'type of whisky' is the definition.
(I've seen this before)
'right on the old' is the wordplay.
'right' becomes 'r' (common abbreviation).
'on' means one lot of letters go next to another.
'the old' becomes 'ye' (**).
'r'+'ye'='RYE'
(Other definitions for rye that I've seen before include "Whisky; Sussex town" , "Cereal plant; whisky" , "Cereal used for making whiskey" , "Cereal grass - Sussex Cinque Port" , "Whiskey (US)" .)