Possible Clues:

• Tree: talk about one
• Talk together about single evergreen tree
• One's usually needled when neighbours go bare
• Eg, pine or fir
• 40-Across source
• Exchange views about one pine, perhaps
• Leader of Indians having powwow around tree
• Fir or pine, for example
• Have discussions about one source of needles
• One typically staying green provided note of hesitation in support of Conservative