An Asian: one's described by that (10)
I believe the answer is:
indonesian
'an asian one's described by that' is the definition.
'Indonesian' can be an answer for 'an asian' (Indonesia is in Asia). I'm unsure of the remainder of the definition.
'an asian one's described by' is the wordplay.
'an asian' becomes 'Indian' (India is in Asia).
'described by' is an insertion indicator (to describe can mean to form an outline).
'indian' placed around 'ones' is 'INDONESIAN'.
Can you help me to learn more?
(Other definitions for indonesian that I've seen before include "Australian neighbour" , "Asian" .)