Final answer:
The nurse should instruct the unit clerk to inform the healthcare provider that the nurse will return the phone call as soon as possible, as taking a prescription order over the phone must be done by a licensed professional for patient safety.
Step-by-step explanation:
In the scenario described, the nurse is preoccupied with an unstable client and thus cannot immediately respond to the healthcare provider on the telephone. The unit clerk, while certified as a medication aide and an unlicensed assistive personnel (UAP), would not have the authority to take a prescription order over the phone. The nurse should instruct the unit clerk to tell the healthcare provider that the nurse will return the phone call as soon as possible. This is in line with proper delegation and communication protocols which maintain patient safety and ensure that medication orders are taken by the appropriate licensed professionals. In health care settings, important tasks such as confirming prescriptions must be carried out by licensed nurses who have the authority and knowledge to understand and verify medical orders, thus ensuring accurate and safe patient care.