Choose nursing team members for constant factor (7)
I believe the answer is:
element
'factor' is the definition.
('element' can be a synonym of 'factor')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for element that I've seen before include "Component - habitat" , "Basic chemical unit" , "Ingredient - small amount" , "Fundamental component" , "piece" .)