After seconds, a youth leaves (5)
I believe the answer is:
salad
'leaves' is the definition.
(salad leaves)
'after seconds a youth' is the wordplay.
'after' says to put letters next to each other.
'seconds' becomes 's'.
'youth' becomes 'lad' (lad means a young man).
's' next to 'a' is 'sa'.
'sa'+'lad'='SALAD'
(Other definitions for salad that I've seen before include "healthy food" , "See 22" , "one gets dressed" , "Raw greens, mainly" , "Raw vegetable dish" .)