Great Asian long-distance runner (5)
I believe the answer is:
indus
'runner' is the definition.
(Indian river)
'great asian long-distance' is the wordplay.
I cannot really understand how this works, but
'distance' could be 'in' and 'in' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for indus that I've seen before include "Long river of Asia" , "banker" , "Largest river of Pakistan" , "Constellation - Pakistan river" , "Asian runner" .)