Opera produced by crew on river (8)
I believe the answer is:
falstaff
'opera' is the definition.
(Verdi opera)
'crew on river' is the wordplay.
'crew' becomes 'staff' (I've seen this before).
'on' says to put letters next to each other.
'river' becomes 'fal' (I've seen this before**).
'staff' after 'fal' is 'FALSTAFF'.
'produced by' acts as a link.
(Other definitions for falstaff that I've seen before include "Sir John in Shakespeare" , "Shak.'s fat knight" , "Shakespeare's rumbustious fat knight" , "Dissolute Shakespearean - Verdi opera" , "Plump character in "Henry IV, Parts I & II"" .)