Commercial enterprise opening beside river in Yorkshire (7)
I believe the answer is:
venture
'commercial enterprise' is the definition.
(I know that venture is a type of commercial enterprise)
'opening beside river in yorkshire' is the wordplay.
'opening' becomes 'vent' (vent is a kind of opening).
'beside' means one lot of letters go next to another (I've seen this in other clues).
'river in yorkshire' becomes 'ure' (River Ure).
'vent'+'ure'='VENTURE'
(Other definitions for venture that I've seen before include "Dare to put forward" , "Undertaking that involves risk" , "Dare, take a chance" , "Enterprise involving risk" , "Risky commercial undertaking" .)