River Test used for business (10)
I believe the answer is:
industrial
'for business' is the definition.
(thesaurus)
'river test' is the wordplay.
'river' becomes 'indus' (Indian river).
'test' becomes 'trial' (synonyms).
'indus'+'trial'='INDUSTRIAL'
'used' acts as a link.
(Other definitions for industrial that I've seen before include "Type of action" , "Characterised by manufacturing processes" , "fabricating things?" , "Inlaid rust (anag.)" , "Rapid social changes, starting in Britain from about 1760" .)