Possible Clues:

• Favourable environment for rapid growth, of rumour say
• Thermostat site, maybe
• Place favourable to growth of intrigue or vice
• Area of rapid development
• Active place
• Place with ideal conditions for rapid growth
• Environment favoring rapid growth
• 'Having had a hot water-bottle in it, there may be trouble brewing there (6)'
• Rapid-growth environment
• Place of rapid development