Athletic drink that's fortified in case of scurvy (6)
I believe the answer is:
sporty
'athletic' is the definition.
(I've seen this before)
'drink that's fortified in case of scurvy' is the wordplay.
'drink that's fortified' becomes 'port' (fortified wine).
'in' indicates putting letters inside.
'case of' means to remove the middle letters (outsides of).
'scurvy' with its middle taken out is 'sy'.
'port' put inside 'sy' is 'SPORTY'.
(Other definitions for sporty that I've seen before include "Describing clothes marked by gaudiness or jazziness" , "Flashy" , "Like athletes" , "preferring to play" , "Given to physical game-playing" .)