Stately home’s new peach melba line? (8,6)
I believe the answer is:
blenheim palace
'stately home's' is the definition.
'new peach melba line?' is the wordplay.
'new' indicates an anagram.
'peach'+'melba'+'line'='peachmelbaline'
'peachmelbaline' with letters rearranged gives 'BLENHEIM PALACE'.
(Other definitions for blenheim palace that I've seen before include "Ducal seat near Woodstock" , "Duke of Marlborough's pile" , "tourist attraction" .)