River Test commercial (10)
I believe the answer is:
industrial
'commercial' is the definition.
(thesaurus)
'river test' is the wordplay.
'river' becomes 'indus' (Indus River is an example**).
'test' becomes 'trial' ('trial' can be a synonym of 'test').
'indus'+'trial'='INDUSTRIAL'
(Other definitions for industrial that I've seen before include "Involved in manufacture" , "Relating to manufacture" , "fabricating things?" , "Characterised by manufacturing processes" , "Rapid social changes, starting in Britain from about 1760" .)