Possible Clues:

• First-class accountants climbing tree
• Mimosa cousin
• Thorny savanna tree
• Tropical tree
• First-rate accountant repeatedly pulled up plant
• Caught teetotallers with spies from garden centre
• Current account at institute is key to what's in garden centre
• Couple of accounts on one note from garden centre
• Thorny ornamental
• First-rate accountant about to turn round plant