Second drink by youth leader, athletic (6)
I believe the answer is:
sporty
'athletic' is the definition.
(athletic means sporty or fit)
'second drink by youth leader' is the wordplay.
'second' becomes 's' (common abbreviation).
'drink' becomes 'port' (port is a kind of drink).
'by' is a charade indicator (letters next to each other).
'leader' indicates taking the first letters.
The initial letter of 'youth' is 'y'.
's'+'port'+'y'='SPORTY'
(Other definitions for sporty that I've seen before include "Describing clothes marked by gaudiness or jazziness" , "Given to physical game-playing" , "preferring to play" , "This 13 [SPICE]" , "Athletic" .)