Island origin of British boxer (4)
I believe the answer is:
bali
'island' is the definition.
(Indonesian island)
'origin of british boxer' is the wordplay.
'origin of' says to take the initial letters.
'boxer' becomes 'Ali' (Muhammad Ali).
The first letter of 'british' is 'b'.
'b'+'ali'='BALI'
(Other definitions for bali that I've seen before include "Island in Indonesia" , "Middle East country" , "Indonesian island, east of Java" , "Bail out of the island" , "mountainous island" .)