Youngster going to a Caribbean republic (4)
I believe the answer is:
cuba
'caribbean republic' is the definition.
(I've seen this before)
'youngster going to a' is the wordplay.
'youngster' becomes 'cub' (I've seen this in other clues**).
'going to' means one lot of letters go next to another.
'cub'+'a'='CUBA'
(Other definitions for cuba that I've seen before include "Largest West Indies island" , "West Indian island" , "Castro's republic" , "Long rum-based drink" , "detached area" .)