Attempt to follow long Asian river? That'll be hard work (8)
I believe the answer is:
industry
'hard work' is the definition.
(being industrious)
'attempt to follow long asian river?' is the wordplay.
'attempt' becomes 'try' (synonyms).
'to follow' is a charade indicator (letters next to each other).
'long asian river?' becomes 'indus' (I've seen this before).
'try' after 'indus' is 'INDUSTRY'.
'that'll be' is the link.
(Other definitions for industry that I've seen before include "Hard work" , "Branch of trade" , "Work (of manufacturing)" , "Diligence" , "Craft" .)