Possible Clues:

• Hardworking institute in Dingle hampered by time
• Painstaking — I tingled (anag)
• Reversing cap, one polite chap is hard-working
• Thorough
• Painstaking cover-up — it protects dope
• Inspector left one figure that's courteous and hard-working
• Cover up for one man in particular
• Hat from East I associated with fellow, painstaking
• Cover up one fellow in particular
• Hard-working inspector fired up, inspiring dope