Copper Jack brought back from island (4)
I believe the answer is:
cuba
'island' is the definition.
(Cuba is an example)
'copper jack brought back' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'jack' becomes 'ab'.
'brought back' says the letters should be written backwards.
'ab' backwards is 'ba'.
'cu'+'ba'='CUBA'
'from' acts as a link.
(Other definitions for cuba that I've seen before include "Caribbean nation" , "neighbour to America" , "Guantanamo Bay island" , "Fidel's place" , "Island N. of Jamaica" .)