Asian banker’s attempt to quit business (5)
I believe the answer is:
indus
'asian banker's' is the definition.
(a river, ie something with 'banks')
'attempt to quit business' is the wordplay.
'attempt' becomes 'try' (synonyms).
'to quit' indicates named letters should be taken away.
'business' becomes 'industry' (industry is a kind of business).
'industry' with 'try' taken away is 'INDUS'.
(Other definitions for indus that I've seen before include "Main river of Pakistan" , "South Asian river" , "9 of Pakistan" , "River of India and Pakistan" , "Sacred flower" .)