Possible Clues:

• See 1 Across
• '60s protest of a sort
• Happy hippie happening
• Hippies' gathering
• 'It's not easy ___ green'
• “Hair” tune
• "Oh, to --- England ..."
• Hippie gathering of a sort
• '___ Green' (Kermit the Frog song)
• 1960s hippie event