Foreign Legion's drink (4,3)
I believe the answer is:
sloe gin
'drink' is the definition.
(sloe gin is a kind of drink)
'foreign legion's' is the wordplay.
'foreign' is an anagram indicator (foreign order of the letters).
'legions' with letters rearranged gives 'SLOE-GIN'.
(Other definitions for sloe gin that I've seen before include "Alcoholic infusion" , "Liqueur made with blackthorn fruit" , "Drink needed" , "Blackthorn-flavoured spirit" , "Legions (anag.)" .)