Island area seen by youngster (4)
I believe the answer is:
cuba
'island' is the definition.
(Cuba is an example)
'area seen by youngster' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'seen by' says to put letters next to each other.
'youngster' becomes 'cub' (young bear).
'a' after 'cub' is 'CUBA'.
(Other definitions for cuba that I've seen before include "Long rum-based drink" , "tropical country" , "detached area" , "Castro's republic" , "neighbour to America" .)