Tease youngster (3)
I believe the answer is:
kid
I believe this is a double definition.
'tease' is the first definition.
(kid can mean to tease or joke)
'youngster' is the second definition.
(I know that kid is a type of youngster)
(Other definitions for kid that I've seen before include "Josh" , "Goat - boy" , "Young animal or child" , "Soft leather" , "Playfully deceive" .)