Hard-working threesome with us on Asian river (11)
I believe the answer is:
industrious
'hard-working' is the definition.
(I've seen this in another clue)
'threesome with us on asian river' is the wordplay.
'threesome' becomes 'trio' (both can mean a group of three).
'with' is a charade indicator (letters next to each other).
'on' means one lot of letters go next to another.
'asian river' becomes 'indus' (the Indus is an Asian river).
'trio'+'us' is 'trious'.
'trious' after 'indus' is 'INDUSTRIOUS'.
(Other definitions for industrious that I've seen before include "Hard working" , "Toiling hard" , "Diligent, hard-working" , "Busy" .)