Possible Clues:

• PM 1970-74
• There's a rotten row at London here
• Overgrown tract
• "Macbeth" setting
• Former prime minister
• Place of gorse/heather
• Sir Edward --, British Prime Minister (1970-74)
• Old PM sets scene for witches' encounter with Macbeth
• Former minister seen in the Carlton or the Athenaeum
• Dwarf shrub or its habitat