Possible Clues:

• Old variety of products, lines coming from fruit plantation
• Might a green house be the trouble with the North, perhaps?
• Round with park officer at end of day in greenhouse
• 'Neither apples, for instance, nor a grey fruit there (8)'
• A hothouse for Protestant extremists?
• Hothouse Kid who played trombone without emotion
• Men cross over rear of the greenhouse
• Greenhouse often with stately home
• Old park keeper's yen for fruit from here?
• Plantation 9 in 6, not 10