Asian writer turned boxer (6)
I believe the answer is:
nepali
'asian' is the definition.
(from Nepal)
'writer turned boxer' is the wordplay.
'writer' becomes 'pen' (something which writes).
'turned' is a reversal indicator.
'boxer' becomes 'Ali' (Muhammad Ali).
'pen' in reverse letter order is 'nep'.
'nep'+'ali'='NEPALI'
(Other definitions for nepali that I've seen before include "Native of a mountainous Hindu kingdom" , "Mountain-dweller" , "Foreigner" , "Kathmandu native" , "Asian national" .)