Kingmaker needs tree for English country home (9)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

you could write this in from the definition, if you spotted that; to parse it you have to know that Richard Neville, 16th Earl of Warwick, was so known, as during the Wars of the Roses he had a big hand in restoring Edward IV and then Henry VI to be King. Then you replace the E in NEVILLE with ASH for tree. And know that Nashville is the home of country music, of course.