Healthy food that's often taken by nurses (5)
I believe the answer is:
pulse
This clue is a double definition.
'healthy food' is the first definition.
(pulses are healthy food)
'that's often taken by nurses' is the second definition.
(a nurse might take a patient's pulse)
(Other definitions for pulse that I've seen before include "Throb, beans" , "Rhythmic throbbing" , "Pound" , "A vital sign turning" , "Beat or throb of heart" .)