Have actually solved it (I think!) but am unable to fully parse a few clues.
5d Rumpole should know all about this rubbish as is found in backward country. Answer has to be STATUTE BAR, and I see the Rumpole part but not the connection to rubbish or a backward country (or country backward).
14a View unfinished version of _The Soldier's Return_ I take to be SIGHT (=view) but don't see the rest of the connection.
15a They're heard in music of Salieri initially not ever discordantly introduced. I have put OVERTUNES with anag. of NOT EVER but perhaps it is OVERTONES after all as either answer yields a leftover letter and I can't tie either decisively to the clue.
Many thanks to all esp. JJ! A big stumbling block was TAT which I only knew as a verb (to make what my grandmother used to call fancywork). Now all is clear. Thank you again!