Drink that's unusual (3)
I believe the answer is:
rum
I believe this clue is a double definition.
'drink' is the first definition.
(rum is a kind of drink)
'unusual' is the second definition.
(I've seen this before)
'that's' acts as a link.
(Other definitions for rum that I've seen before include "An odd kind of drink made from molasses" , "Funny" , "Odd sort of drink" , "Odd spirit from sugar cane" , "Odd kind of drink for sailor" .)