American sub oddly capsized in the drink (8)
I believe the answer is:
absinthe
'drink' is the definition.
(absinthe is a kind of drink)
'american sub oddly capsized in the' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'capsized' is a reversal indicator.
The alternating letters of 'sub' are 'sb'.
'sb' back-to-front is 'bs'.
'a'+'bs'+'in'+'the'='ABSINTHE'
(Other definitions for absinthe that I've seen before include "Strong green liqueur, lethal when made with wormwood" , "Strong green alcoholic drink" , "alcohol" , "Potent green gin-type liquor - wormwood" , "Bathes in strong liquour, strangely" .)