Arabs, in theory, will secrete potent drink (8)
I believe the answer is:
absinthe
'potent drink' is the definition.
(absinthe is a strong alcoholic drink)
'arabs in theory will secrete' is the wordplay.
'secrete' indicates the answer is hidden within the clue (I've seen 'secreted' mean this).
'ABSINTHE' can be found hidden inside 'arabs in theory will'.
(Other definitions for absinthe that I've seen before include "Green liqueur flavoured with wormwood and anise" , "Strong green liqueur, lethal when made with wormwood" , "Potent green gin-type liquor - wormwood" , "Bathes in strong liquour, strangely" , "alcohol" .)